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1

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

2

Two new types of laser doppler flowmeters prototypes validation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A fluxometria laser Doppler (LDF) é uma técnica para avaliação em tempo real do fluxo microcirculatório em tecidos biológicos. Esta técnica pode ser usada para monitorização não invasiva da microcirculação (por exemplo, avaliação da perfusão na pele), ou para monitorização da perfusão de forma invasiva (por exemplo, avaliação da perfusão no cérebro). Nesta tese, pretende-se acrescentar ao estado da arte da LDF, quando aplicada à monitorização não invasiva da perfu...

Campos, Rita Helena Pinto Oliveira

2011-01-01

3

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. PMID:22462941

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

2012-03-01

4

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

5

Monitoring of traumatic process after hernioplasty by allografts using laser doppler flowmeter  

International Nuclear Information System (INIS)

Full text: This is a comparative analysis of correlation between pathological phenomena of hemomicrom circulation at local trophic level of healing postoperative wounds by primary and secondary intention after hernioplasty by biomembranes (allografts) and by artificial reticular endoprosthesis. In this study two groups of patients were formed: I group (77 patients) underwent hernioplasty by implantation of biomembranes (Tutoplast allografts Fascia temporalis, Dermis); II group (81 patients) had hernioplasty using artificial reticular endoprosthesis. Comparative complex investigation of healing postoperative wounds was done by laser Doppler flowmeter, which allows fairly evaluating staging of traumatic process in 158 patients aging from 20 to 73 years, male, that underwent surgical treatments of inguinal hernia. In all patients traditional surgical technique using non-tension plasty methods for anterior abdominal wall was applied using above-mentioned materials. In first group wound healing took place by primary intention in all 77 patients and on amplitude-frequency spectrum of LDF charts happened by 4 phases: 1) reaction to trauma; 2) initial regeneration; 3) wound consolidation; 4) scar organization. In the second group - in 75 cases wound healing also took place by primary intention, but in 6 cases a secondary intention happened, which consisted on amplitude-frequency spectrum of LDF charts of 6 phases: 1) inflammation, 2) wound clearance from necrotic suppurative masses; 3) initial regeneration; 4) forming of granulations; 5) wound consolidation; 6) scar reorganization. To improve results of surgical treatment in patients with hernia it is needed to approach the choice of material for hernioplasty differentially depending hemodynamic type of microcirculation. Characteristics of vascular tissue system of future operative area directly influence the course of traumatic process in postoperative follow-up. Monitoring of traumatic process following hernioplasty by allografts done by laser Doppler flowmeter allows prognosing the course of early postoperative follow-up and to diagnosing complications in advance. (Author)

2008-06-02

6

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

7

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2003-01-01

8

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

1983-01-01

9

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)

1982-03-26

10

Laser doppler spectroscopy  

International Nuclear Information System (INIS)

The main objects of this paper will be to review the latest developments in laser Doppler techniques as well as the results of cell electrophoretic studies. Although the first cell mobility measurements were done in physiological saline, it has not been until recently that high resolution Doppler measurements of cells in high salt conditions has become routine. This important technical advance has been due to improvements in electrode materials, electrophoresis chamber designs, and heterodyne optics. These topics are considered in detail in Section IV and Section V. In Section VI various laser Doppler approaches are compared with each other as well as with microscopic, free flow analytic, and density gradient techniques. Particle studies are reviewed in Section VII and blood cell studies in the remaining sections of the paper. (orig.)

1981-01-01

11

Quantitative Laser Doppler Flowmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laser Doppler flowmetry (LDF) is virtually the only non-invasive technique, except for other laser speckle based techniques, that enables estimation of the microcirculatory blood flow. The technique was introduced into the field of biomedical engineering in the 1970s, and a rapid evolvement followed during the 1980s with fiber based systems and improved signal analysis. The first imaging systems were presented in the beginning of the 1990s. Conventional LDF, although unique in many aspects an...

2009-01-01

12

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

13

Modeling and processing of laser Doppler reactive hyperaemia signal  

Science.gov (United States)

Laser Doppler flowmetry is a non-invasive method used in the medical domain to monitor the microvascular blood cell perfusion through tissue. Most commercial laser Doppler flowmeters use an algorithm calculating the first moment of the power spectral density to give the perfusion value. Many clinical applications measure the perfusion after a vascular provocation such as a vascular occlusion. The response obtained is then called reactive hyperaemia. Target pathologies include diabetes, hypertension and peripheral arterial occlusive diseases. In order to have a deeper knowledge on reactive hyperaemia acquired by the laser Doppler technique, the present work first proposes two models (one analytical and one numerical) of the observed phenomenon. Then, a study on the multiple scattering between photons and red blood cells occurring during reactive hyperaemia is carried out. Finally, a signal processing that improves the diagnosis of peripheral arterial occlusive diseases is presented.

Humeau, Anne; Saumet, Jean-Louis; L'Huiller, Jean-Pierre

2003-07-01

14

Laser doppler perfusion imaging  

International Nuclear Information System (INIS)

Recording of tissue perfusion is important in assessing the influence of peripheral vascular diseases on the microcirculation. This thesis reports on a laser doppler perfusion imager based on dynamic light scattering in tissue. When a low power He-Ne laser beam sequentally scans the tissue, moving blood cells generate doppler components in the back-scattered light. A fraction of this light is detected by a photodetector and converted into an electrical signal. In the processor, a signal proportional to the tissue perfusion at each measurement site is calculated and stored. When the scanning procedure is completed, a color-coded perfusion image is presented on a monitor. To convert important aspects of the perfusion image into more quantitative parameters, data analysis functions are implemented in the software. A theory describing the dependence of the distance between individual measurement points and detector on the system amplification factor is proposed and correction algorithms are presented. The performance of the laser doppler perfusion imager was evaluated using a flow simulator. A linear relationship between processor output signal and flow through the simulator was demonstrated for blood cell concentrations below 0.2%. The median sampling depth of the laser beam was simulated by a Monte Carlo technique and estimated to 235 ?m. The perfusion imager has been used in the clinic to study perfusion changes in port wine stains treated with argon laser and to investigate the intensity and extension of the cutaneous axon reflex response after electrical nerve stimulation. The fact that perfusion can be visualized without touching the tissue implies elimination of sterilization problems, thus simplifying clinical investigations of perfusion in association with diagnosis and treatment of peripheral vascular diseases. 22 refs

1992-01-01

15

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)

2008-11-24

16

Laser Doppler Imaging of Microflow  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

2006-01-01

17

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

18

Anemometrie Laser a Effect Doppler Miniaturise a Diode Laser (Laser Doppler Anemometer Miniaturized with Diode Laser).  

Science.gov (United States)

An 11 by 4 by 4 cm miniaturized laser Doppler anemometer system using laser diodes is described. The system was tested with a velocity profile of a free jet. The use of synthetic resin optics would improve the miniaturization and reduce the cost of this t...

S. Damp H. Pfeifer

1989-01-01

19

Compensating For Doppler Shift In Laser Instrumentation  

Science.gov (United States)

Electronic tuning system continually adjusts frequency of tunable diode laser to compensate for Doppler shift caused by motion of transmitter or receiver containing laser. Doppler-shift-compensating system intended primarily for use in transmitter or receiver of laser remote-sensing or communication system to keep frequency of received signal within frequency range of narrow-band-pass filter. By use of narrow-band filter (instead of wide-band filter required in absence of Doppler compensation), signal-to-noise ratio of laser system increased. Thus, less-powerful transmitter usable.

Schwemmer, Geary K.

1990-01-01

20

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)

2008-08-01

 
 
 
 
21

Doppler velocimeter for laser accelerated targets  

International Nuclear Information System (INIS)

A doppler velocimeter utilizing a spectrograph and a short pulse laser probe is described which provides good spatial (20 ?m) and subnanosecond temporal resolution. This system has been used to measure the velocity profiles of targets ablatively accelerated to very high velocities by a high power laser beam. A unique aspect of this velocimeter is that the doppler wavelength shifts are measured directly rather than employing interferometric techniques

1980-01-01

22

Turbulence measurements using the laser Doppler velocimeter.  

Science.gov (United States)

The photomultiplier signal representing the axial velocity of water within a glass pipe is considered. It is shown that with proper analysis of the photomultiplier signal, the turbulent information that can be obtained in liquid flows is equivalent to results obtained in recent hot film studies. In shear flows the signal from the laser Doppler velocimeter contains additional information which may be related to the average shear.

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

1971-01-01

23

Developments in laser Doppler blood perfusion monitoring  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper reviews the development and use of laser Doppler perfusion monitors and imagers. Despite their great success and almost universal applicability in microcirculation research, they have had great difficulty in converting to widespread clinical application. The enormous interest in microvascular blood perfusion coupled with the 'ease of use' of the technique has led to 2000+ publications citing its use. However, useful results can only be achieved with an understanding of the basic pr...

2003-01-01

24

Signal broadening in the laser Doppler velocimeter.  

Science.gov (United States)

Critical review of a recent paper in which Denison, Stevenson, and Fox (1971) discussed the sources of spectral broadening in the laser Doppler velocimeter. It is pointed out that, in their discussion, the above-mentioned authors indicated that the spread in wave vectors of the incident and detected fields and the finite length of time a scattering center stayed in the sample volume each contributed separately and independently to the observed spectral width of the scattered radiation. This statement is termed incorrect, and it is shown that the two effects are one and the same.

Angus, J. C.; Edwards, R. V.; Dunning, J. W., Jr.

1971-01-01

25

Pulsed laser Doppler measurements of wind shear  

Science.gov (United States)

There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

1979-01-01

26

Laser Doppler vibrometry: new ENT applications  

Science.gov (United States)

Common audiometry often does not really allow a reliable and objective differential diagnosis of hearing disorders such as otosclerosis, adhesive otitis, ossicular interruption or tinnitus, even though several methods might be used complementarily. In recent years, some experimental studies on middle ear mechanics established laser Doppler vibrometry (LDV) as a useful method allowing objective measurement of human tympanic membrane displacement. The present study on LDV investigated the clinical use of this new method under physiological conditions. LDV proved to be a fast, reproducible, non-invasive and very sensitive instrument to characterize ear-drum vibrations in various middle ear dysfunctions, except in tinnitus patients. For future applications, improved optical characteristics of the vibrometer might result in a better differential diagnosis of subjective and objective tinnitus, otoacoustic emissions or Morbus Meniere.

Stasche, Norbert; Baermann, M.; Kempe, C.; Hoermann, Karl; Foth, Hans-Jochen

1996-12-01

27

Laser Doppler instrument measures fluid velocity without reference beam  

Science.gov (United States)

Fluid velocity is measured by focusing laser beam on moving fluid and measuring Doppler shift in frequency which results when radiation is scattered by particles either originally present or deliberately injected into moving fluid.

Bourquin, K. R.; Shigemoto, F. H.

1971-01-01

28

Blood flow measurement by laser Doppler method in orofacial region  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 reflecte...

Grga ?urica; Dželetovi? Bojan; Živkovi? Slavoljub; Kršljak Elena

2010-01-01

29

Diode-pumped alexandrite laser for DIAL and Doppler lidar  

Science.gov (United States)

The problem of laser selection for spaceflight DIAL or Doppler lidar is considered. Spaceflight lidar requires tens of watts of laser output, and the low efficiency of lasers imposes costly burdens on the spacecraft platform. DIAL requires a tunable laser, and Doppler an ultraviolet laser, so the high efficiency of the Nd:YAG laser is compromised. The alexandrite laser can in principle provide higher systems efficiency for DIAL or Doppler than the Nd:YAG, being intrinsically tunable, and capable of reaching the ultraviolet with frequency doubling. High power 680 nm laser diodes are now available with sufficient power to pump alexandrite to the necessary power levels. A Q-switched laser configuration is modeled to obtain a projection laser efficiency of 13 percent. A more conservative estimate is 3.5 percent, well below the 9 percent achieved with Nd:YAG. Considering the energy savings through intrinsic tunability, frequency doubling to the ultraviolet, and extremely narrow spectral linewidth, a Doppler wind lidar system based on the alexandrite laser would have four to nine times the efficiency of the Nd:YAG alternative.

McKay, Jack A.; Wilkerson, Thomas D.

1997-10-01

30

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

31

Measurement of microvascular blood flow in cancellous bone using laser Doppler flowmetry and 133Xe-clearance  

International Nuclear Information System (INIS)

Blood flow in cancelleous bone with varying vascular density was investigated simultaneously with Laser Doppler Flowmeter (LDF) and 113Xe-clearance. The cancellous bone subapical to 2 contralateral incisors in the mandibles of 17 young pigs was used as an experimental model. Light from a 2 mW He-Ne-laser was guided through an optical fibre to a flowmeter probe. Stainless steel probe-holders firmly inserted in the pulpal canals of the two incisors served as the probe entrance to cancellous bone for blood flow recording. Due to the Doppler effect, the light scattered by circulating blood cells undergoes a frequency shift. The back-scattered light picked up by optical fibres in the probe, was guided to a photosensitive device, where it was demodulated. After signal processing, a signal referred to as the Blood Flow Value (BFV) was recorded on a pen recorder. Rhythmical variations (vasomotion) in BFV with frequencies from 2-11 cycles/min were observed in 6% of recordings made initially after probeholder implantation, and in 34% of the recordings made 5 weeks later. On this occasion, a marked increase in BFV was recorded. Histological examination showed increased vascularity in the bone tissue. The reproducibility error of LDF was 7.4% and temporal changes in BFV, apart from vasomotion, were 8.3%, provided no injections or manipulations of the probe were made. Spatial variations in BFV were found to be related to the vascular density. 2 successive recordings by LDF from the same bone area were highly correlated (r=0.98). The corresponding figure for 2 logarithmic decay rates of locally injected 133Xe was 0.76. No correlation between BFV and 133Xe-clearance could be demonstrated. (author)

1983-01-01

32

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

33

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

34

Processor operated correlator with applications to laser Doppler signals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A 64-channel correlator is designed with application to the processing of laser Doppler anemometry signals in the range 200 Hz to 250 kHz. The correlator is processor operated to enable the consecutive sampling of 448 correlation functions at a rate up to 500 Hz. Software is described to identify a Doppler frequency from each correlation and the system is especially designed for transient flow signals. Doppler frequencies are determined with an accuracy of about 0.1%. Review of Scientific Ins...

Bisgaard, C.; Johnsen, B.; Hassager, Ole

2009-01-01

35

Measurement depth and volume in laser Doppler flowmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new method for estimating the measurement depth and volume in laser Doppler flowmetry (LDF) is presented. The method is based on Monte Carlo simulations of light propagation in tissue. The contribution from each individual Doppler shift is calculated and thereby multiple Doppler shifts are handled correctly. Different LDF setups for both probe based (0.0, 0.25, 0.5, and 1.2 mm source-detector separation) and imaging systems (0.5 and 2.0 mm beam diameter) are considered, at the wavelengths 5...

Fredriksson, Ingemar; Larsson, Marcus; Stro?mberg, Tomas

2009-01-01

36

Non-intrusive Shock Measurements Using Laser Doppler Vibrometers  

Science.gov (United States)

Stud mount accelerometers are widely used by the aerospace industry to measure shock environments during hardware qualification. The commonly used contact-based sensors, however, interfere with the shock waves and distort the acquired signature, which is a concern not actively discussed in the community. To alleviate these interference issues, engineers at the Jet Propulsion Laboratory are investigating the use of non-intrusive sensors, specifically Laser Doppler Vibrometers, as alternatives to the stud mounted accelerometers. This paper will describe shock simulation tests completed at the Jet Propulsion Laboratory, compare the measurements from stud mounted accelerometers and Laser Doppler Vibrometers, and discuss the advantages and disadvantages of introducing Laser Doppler Vibrometers as alternative sensors for measuring shock environments.

Statham, Shannon M.; Kolaini, Ali R.

2012-01-01

37

Fano-Doppler laser cooling of hybrid nanostructures.  

Science.gov (United States)

Laser cooling the center-of-mass motion of systems that exhibit Fano resonances is discussed. We find that cooling occurs for red or blue detuning of the laser frequency from resonance depending on the Fano factor associated with the resonance. The combination of the Doppler effect with the radiation cross-section quenching typical of quantum interference yields temperatures below the conventional Doppler limit. This scheme opens perspectives for controlling the motion of mesoscopic systems such as hybrid nanostructures at the quantum regime and the exploration of motional nonclassical states at the nanoscale. PMID:21806014

Ridolfo, Alessandro; Saija, Rosalba; Savasta, Salvatore; Jones, Philip H; Iatì, Maria Antonia; Maragò, Onofrio M

2011-09-27

38

Laser Doppler velocimetry based on the photoacoustic effect in a CO2 laser  

International Nuclear Information System (INIS)

We report a simple laser Doppler velocimeter in which the photoacoustic effect was used to measure the rotation wheel speed. A Doppler signal, caused by mixing a returning wave with an originally existing wave inside the CO2 laser cavity, was detected using a microphone in the laser tube. Frequency of the microphone output was in proportion to the rotation speed of a wheel and is dependent on the cosine of the angle between the direction of the laser beam and tangent of wheel velocity. A Doppler-shifted frequency as high as 34 kHz was detected using this method. A frequency response of a few megahertz is expected from the laser Doppler velocimeter based on the photoacoustic effect in a CO2 laser by using a wider bandwidth microphone

2005-02-01

39

Effective particle size range in laser-Doppler anemometry  

International Nuclear Information System (INIS)

The present paper points out that all existing laser-Doppler anemometer systems do not only operate within a finite range of Doppler frequencies but also work within a relatively narrow range of signal amplitudes. It is shown that this corresponds to a finite, and usually to an extremely small, range of particle diameters which contributes to the final LDA measurements. The investigation results in conclusions regarding optimum particle size distributions for laser-Doppler anemometry. If fluid velocity measurements are attempted rather than particle velocity measurements, the particles still have to satisfy well known size requirements that are flow, fluid and particle density dependent. The experimental study employs a combined optical system for simultaneous measurements of particle velocity, particle size and particle concentration. The system is used to measure those particles of a spectrum of oil droplets that contribute to the validated signal output of counter and transient recorder based LDA-electronic signal processing systems. (orig./HP)

1987-01-01

40

Dual beam translator for use in Laser Doppler anemometry  

Energy Technology Data Exchange (ETDEWEB)

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

 
 
 
 
41

Retrospective steam flowmetering  

Energy Technology Data Exchange (ETDEWEB)

Detailed metering of steam usage is becoming increasingly important, and the desire to install steam flowmeters in pre-existing pipework ('retrospective installation') is growing accordingly. The types of flowmeter commonly used for steam are here reviewed, followed by a brief discussion of their use in retrospective applications. It is argued that there would be a substantial market for a simple 'clip-on' steam flowmeter if one could be developed.

Bertinat, M.P.

1987-11-01

42

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

DEFF Research Database (Denmark)

n 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 â?? 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 velocimeterâ??s performance

Rodrigo, Peter John; Pedersen, Christian

2014-01-01

43

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

44

Laser Doppler vibrometer employing active frequency feedback  

International Nuclear Information System (INIS)

We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well

2008-09-20

45

Fabrication of Portable Laser Doppler Velocimetry and Speckle Velocimetry  

Energy Technology Data Exchange (ETDEWEB)

The laser power stability and laser frequency stability of various liquid lasers and gas lasers were affected by the fluid velocity of a laser active medium. The control of laser cavities in order to reduced the fluctuation of laser powers have been studied. However, inspit of these methods, the power instability of the multi-step dye laser system for high power was 5-10 %. The main reason was the flow instabilities of laser active madium. Then we have been studied the measurement of fluid velocities and velocity distributions of the dye fluid in a dye cell by using a ready-made laser Doppler velocimeter(LDV), which is a good sensor for the measurement of fluid velocities with high accuracy. However, the ready-made LDV has a several disadvantages of big sizes, large optical probes, high prices, difficulties of the moving, etc.. In this study, we have studies for the fabrication of small potable LDV with small optical probes using a high power DRB laser diode and single mode optical fibers for the measurement of fluid velocities from 1 cm/s to 1 m/s. 28 refs., 1 tabs., 53 figs. (author)

Jo, Jae Hong; Chang, S.; Kim, B. J.; Lee, J. C.; Choi, W. H.; Kim, J. T. [Hannam University, Taejon (Korea, Republic of)

1997-07-01

46

Is there a difference between laser speckle and laser Doppler in depth sensitivity?  

Science.gov (United States)

Laser speckle and laser Doppler perfusion measurements apply different analyses to the same physical phenomenon and so should produce the same results. However, there is some evidence that laser Doppler can measure perfusion at greater depths than laser speckle. Using phantom measurements and comparison to spatially modulated imaging, we show why this might be the case. Various implementations of imaging laser Doppler and speckle systems have different optical setups, producing different effective distances between the illumination and detector points on the surface of the tissue. Separating the effective source and detector regions in tissue measurements biases the measurements towards deeper tissues, and when the effective source and detector regions coincide, the measurement is biased towards surface tissues. Probe-based or scanning laser Doppler systems with point illumination can separate the source and detector regions to interrogate deeper tissues, while whole-field imaging laser Doppler systems and laser speckle contrast systems have broad illumination covering the measurement areas. The volume of tissue informing a measurement at any point in a whole-field system, and hence the depth sensitivity, is determined by the optical properties of the tissue at the working wavelength.

Thompson, O. B.; Hirst, E. R.; Andrews, M. K.

2011-02-01

47

[Microcirculatory evaluation of the early diabetic foot syndrome using laser doppler].  

Science.gov (United States)

Recognition of early microcirculatory disturbances in feet of diabetics may facilitate the pathogenic interpretation of the diabetic foot syndrome, selection of the patients at risk of developing clinical problems and serve as the base for designing the preventive measures. This could be particularly true in diabetics with peripheral neuropathy. Therefore the study aimed at the assessment of functional parameters of the foot microcirculation in IDDM patients presenting signs of peripheral neuropathy but without any symptoms of the diabetic foot syndrome was undertaken. For comparison 20 IDDM subjects with the signs of peripheral neuropathy and 10 IDDM subjects without this complication were studied both clinically and metabolically. All of them underwent the examination of microcirculation of the feet with the use of Laser Doppler Flowmeter. The parameters measured were: resting blood flow, post-occlusive, hyperemic response, flow change after heating to 44 degrees C and the flow on dependency. In IDDM subjects with peripheral neuropathy the following functional microcirculatory abnormalities were found: delay and decrease in post-occlusive, hyperemic response (4.5 +/- 1.8 s in neuropathic vs 0.5 +/- 2.4 s in non-neuropathic IDDM patients), decrease of the peak flow (36 +/- 7.0 PU in non neuropathic vs 18 +/- 5.0 PU in neuropathic IDDM patients) and also impairment of the response of the skin flow to focal heating peak flow at 44 degrees C (48 +/- 7.0 PU vs 12 +/- 3.0 PU in non neuropathic IDDM patients). Also the venoarteriolar reflex measured as the ratio of resting to standing flow in the feet skin was significantly decreased (80% in non-neuropathic versus 35% in neuropathic IDDM patients). Conclusion: Laser Doppler Flowmetry discovers the very early functional abnormalities in the microcirculation of the skin in the feet of IDDM with peripheral neuropathy, when none of the typical symptoms of the diabetic foot syndrome is present. It points to the significance of the relation between neuropathic and microcirculatory disturbances in the early pathogenesis of diabetic foot syndrome. PMID:9296891

Walewski, J; Tato?, J; Kuczerowski, R; Buraczewska, B; Czech, A

1997-01-01

48

Laser Doppler vibrometry with acoustooptic frequency shift  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes our experiments and investigations on vibration measurements by laser interferometers. The main objective was to build a simple heterodyne interferometer which would allow vibrations of objects with light scattering surface to be measured. The optimisation procedure of optical setup, basic heterodyne interferometer and results are presented.

Krzysztof M. Abramski

2004-01-01

49

Measuring velocities by laser Doppler interferometry  

International Nuclear Information System (INIS)

The advanced development of two optical velocimeters, the VISAR (velocity interferometer system for any reflector) and the Fabry--Perot systems, that greatly increase the sensitivity and resolution of measurements of shock and particle velocities is described. Both operate by measuring the Doppler shift in the frequency of light reflected from the moving body. In either case the system output produces velocity information directly, and this information can then be integrated to determine the position at any time. The VISAR output is recorded on fast oscilloscopes that can be set to observe different portions of the velocity history. The Fabry--Perot system has less flexibility, sensitivity, and time resolution than the VISAR, but its output is recorded directly on photographic film and is much simpler to analyze. Both systems are compatible with most of our other diagnostics and measure velocities to about 1% accuracy with time resolutions of a few nanoseconds. They can record velocity features over distances as small as 2.5 ?m even though the interferometers may be located over 30 m from the test object

1979-03-01

50

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

51

Dynamic fringe broadening in multiple line laser Doppler velocimetry  

Energy Technology Data Exchange (ETDEWEB)

The recently reported multiple line laser Doppler velocimetry technique involves a compromise between laser power and fringe broadening. The present work analyzes the broadening as a function of both the target velocity and the separations of the Fabry-Perot etalons, which in this work do not have to be the same. It is shown that the overlap finesse broadening, which is defined as the ratio of the frequency separation between fringes to the overlap broadening, depends on the number of free spectral ranges that have occurred due to the velocity of the reflecting target.

Goosman, D.R. (Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (US))

1990-01-01

52

Sub-Doppler laser spectroscopy of small molecules  

International Nuclear Information System (INIS)

Three different techniques of laser spectroscopy with sub-Doppler resolution are discussed which have been applied to the investigation of diatomic and triatomic molecules. These are linear laser spectroscopy in collimated molecular beams, polarization spectroscopy and a combination of both methods with optical-optical double resonance techniques. The methods are illustrated by high resolution spectra of the molecules NaK, Cs2 and NO2. A section on time resolved spectroscopy, applied to lifetime measurements and to the determination of collision induced relaxation processes concludes the paper. (orig.)

1980-01-01

53

Laser Doppler velocity simulator. [to induce frequency shift  

Science.gov (United States)

A method and apparatus for inducing a Doppler frequency shift in a reference beam laser velocimeter light beam to simulate target velocity are described. The light beam is passed through a rotating refractive transparent block positioned between two reference points along the beam which results in a continuous change in the light beam optical path length between the reference points according to a known function. The velocity indicated by the laser velocimeter is compared to the known simulated velocity function for velocimeter testing and calibration.

Franke, J. M. (inventor)

1979-01-01

54

Laser Doppler velocimeter with a novel optical fiber probe.  

Science.gov (United States)

A practical laser Doppler velocimeter with optical fibers in the whole system was developed. The novel optical probe designed for this LDV is constructed of a graded-index rod lens attached to the end of an optical fiber. Since the laser beam from the probe is well collimated, the velocity accuracy and sensitivity are significantly improved. Mechanical vibration measurements were also carried out with this LDV; vibration amplitude down to 1.0 microm p-p can be measured at a frequency of 120 Hz with high accuracy. PMID:20332971

Kyuma, K; Tai, S; Hamanaka, K; Nunoshita, M

1981-07-15

55

Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central par...

2012-01-01

56

Doppler shift of laser light reflected from expanding plasmas  

International Nuclear Information System (INIS)

The Doppler shift of light reflected from a plane stratified expanding plasma is analyzed. Nonlinear effects are not considered and oblique incidence is restricted to the case of s polarization. The frequency shift is shown to consist of two components, one due to the motion of the reflecting surface, and another due to plasma flow through that surface. The shifts have a different dependence on the angle of incidence. Typically, the two contributions are comparable in laser fusion applications, being of order delta?/?approx.c/sub s//capprox.10"-"3, where c/sub s/ = (Z-italic T/sub e//M)/sup 1/2/ is the ion sound speed in the underdense plasma. In general, the Doppler shift has a time variation which induces a bandwidth in the reflected wave

1981-01-01

57

Side effects of laser-tissue interaction studied by laser Doppler vibrometry  

Science.gov (United States)

Mechanical effects that amy damage tissue were measured by laser doppler vibrometry. The results on the recoil momentum illustrate the laser parameters under which laser survey of organs with delicate structures becomes dangerous. One example is the acceleration of the tiny middle ear bones. In the case of an intact ossicular chain, the motion of a middle ear bone is transferred to the inner ear. The second topic is related to eye surgery. Removing or cutting of membranes, the lens or the vitreous body by pulsed lasers is often associated with the formation of laser induced cavitation bubbles. The collapse of these bubbles generates pressure shock waves propagation through the eye. Laser Doppler vibrometry was used to monitor the shock wave induced velocity of the sclera.

Foth, Hans-Jochen; Meyer, Dirk; Stoeckel, Thomas

2000-05-01

58

Mucosal blood flow measurements using laser Doppler perfusion monitoring  

Directory of Open Access Journals (Sweden)

Full Text Available Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insufficiency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of peripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastrointestinal (GI tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results.

Dag Arne Lihaug Hoff, Hans Gregersen, Jan Gunnar Hatlebakk

2009-01-01

59

Solid state and fibre optic laser doppler velocimeters  

Science.gov (United States)

Laser Doppler velocimetry (LDV) has become established as an important technique for the measurement of velocities of macroscopic objects and fluids: the dynamic range is large (˜10 -6-10 5 ms -1) and the measurement is absolute and non-invasive. However, the size and cost of LDV has restricted its use in some areas. This paper presents two separate approaches to reduce these problems: we describe a compact LDV system incorporating a solid state laser diode and also an investigation of the feasibility of a fibre optic LDV system in which the conventional optical components are replaced by fibre optics. The experimental arrangement used for the solid state LDV system was of the Doppler difference type; i.e. a system of parallel interference fringes is focused in the measurement volume, so that a particle passing through this volume produces a scattered light signal which is intensity modulated. In its simplest form, the technique cannot determine the direction of motion of the particle, but this difficulty may be overcome by causing the fringes to 'move' within the measurement volume with known velocity. In the present experiments, the laser output frequency was modulated by modulating its drive current; since the path lengths of the two beams interfering in the measurement volume were unequal, fringe motion was achieved. The fibre optic LDV experiment was also of the Doppler difference type, and it was demonstrated that the necessary stabilised interference fringe system could be projected using a fibre optic system. An electronic servo was devised to compensate for the random differential thermal drifts in the fibres which would otherwise have produced unacceptable drifts in the fringe pattern.

Jones, J. D. C.; Jackson, D. A.; Corke, M.; Kersey, A. D.

60

Sub-Doppler Laser Cooling of Fermionic K-40 Atoms  

CERN Multimedia

We report laser cooling of fermionic K-40 atoms, with temperatures down to (15 +/- 5) microK, for an enriched sample trapped in a MOT and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of two of the lowest realizable rms velocity (~3.5v rec) in 3D optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of K-40 atoms.

Modugno, G; Hannaford, P; Roati, G; Inguscio, M

1999-01-01

 
 
 
 
61

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

62

Turbulent transport measurements with a laser Doppler velocimeter.  

Science.gov (United States)

The power spectrum of phototube current from a laser Doppler velocimeter operating in the heterodyne mode has been computed. The spectral width and shape predicted by the theory are in agreement with experiment. For normal operating parameters the time-average spectrum contains information only for times shorter than the Lagrangian-integral time scale of the turbulence. To examine the long-time behavior, one must use either extremely small scattering angles, much-longer-wavelength radiation, or a different mode of signal analysis, e.g., FM detection.

Edwards, R. V.; Angus, J. C.; Dunning, J. W., Jr.

1972-01-01

63

Laser doppler measurements of flow in a rod bundle  

International Nuclear Information System (INIS)

A two component laser doppler velocimeter with polarized beams and frequency shift was used to measure the turbulent flow field for axial flow between the rods of a nine rod, square pitch rod bundle. Parameters measured include mean axial and lateral velocities, turbulence intensities and the friction factor. The axial velocities for 10 000 to 40 000 Reynolds number are slightly higher than those reported by Rowe. The maximum lateral velocities measured are about 1% of the bulk velocity; somewhat larger than suggested by earlier authors. Axial and lateral turbulence intensities are larger than those in pipe flows. (orig.)

1983-01-01

64

Laser doppler anemometry in single- and two-phase flows  

International Nuclear Information System (INIS)

The present report gives an introduction into laser-Doppler anemometry and tries to explain the basic physical principles of this measuring technique. Moire fringe patterns are used in order to visually model LDA-signals and to explain the basic difference in optical systems. It is pointed out that LDA measurements in highly turbulent flows and in two-phase flows should be attempted with direction sensitive instruments only. Some of the optical systems developed by the author and his collaborators are introduced and their functioning in measurements is demonstrated. These measurements embrace investigations in a number of single-phase flows including flames. (orig.)

1976-07-01

65

Real-time full field laser Doppler imaging  

Science.gov (United States)

We present a full field laser Doppler imaging instrument that enables real-time in vivo assessment of blood flow in dermal tissue and skin. The instrument monitors the blood perfusion in an area of about 50cm2 with 480 × 480 pixels per frame at a rate of 12-14 frames per second. Smaller frames can be monitored at much higher frame rates. We recorded the microcirculation in healthy skin before, during and after arterial occlusion. In initial clinical case studies, we imaged the microcirculation in burned skin and monitored the recovery of blood flow in a skin flap during reconstructive surgery indicating the high potential of LDI for clinical applications.

Leutenegger, Marcel; Harbi, Pascal; Thacher, Tyler; Raffoul, Wassim; Lasser, Theo

2012-06-01

66

Novel measure for the calibration of laser Doppler flowmetry devices  

Science.gov (United States)

The metrological basis for optical non-invasive diagnostic devices is an unresolved issue. A major challenge for laser Doppler flowmetry (LDF) is the need to compare the outputs from individual devices and various manufacturers to identify variations useful in clinical diagnostics. The most common methods for instrument calibration are simulants or phantoms composed of colloids of light-scattering particles which simulate the motion of red blood cells based on Brownian motion. However, such systems have limited accuracy or stability and cannot calibrate for the known rhythmic components of perfusion (0.0095-1.6 Hz). To solve this problem, we propose the design of a novel technique based on the simulation of moving particles using an electromechanical transducer, in which a precision piezoelectric actuator is used (e.g., P-602.8SL with maximum movement less than 1 mm). In this system, Doppler shift is generated in the layered structure of different solid materials with different optical light diffusing properties. This comprises a fixed, light transparent upper plane-parallel plate and an oscillating fluoroplastic (PTFE) disk. Preliminary studies on this experimental setup using the LDF-channel of a "LAKK-M" system demonstrated the detection of the linear portion (0-10 Hz with a maximum signal corresponding to Doppler shift of about 20 kHz) of the LDF-signal from the oscillating frequency of the moving layer. The results suggest the possibility of applying this technique for the calibration of LDF devices.

Dunaev, Andrey V.; Zherebtsov, Evgeny A.; Rogatkin, Dmitrii A.; Stewart, Neil A.; Sokolovski, Sergei G.; Rafailov, Edik U.

2014-03-01

67

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

68

Fiber-optic laser Doppler turbine tip clearance probe  

Science.gov (United States)

A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 ?m, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

69

Measuring with laser Doppler vibrometer on moving frame (LDVMF)  

Science.gov (United States)

Structural dynamic gives insight into structural properties such as mass, eigenfrequencies, eigenmodes, modal damping and strain distribution and can be utilized in structural health monitoring, dynamic sub-structuring, etc. In this context structural vibration is measured and used. The measurement is done by means of conventional sensors such as accelerometers or non destructively using Laser Doppler Vibrometer (LDV), for instance. The non-destructive, non-contact measurement techniques preserve the integrity of the structure and don't add mass and stiffness to the structure under test. When one deals with civil structures such as rail and road ways, pipelines and catenary the importance of these techniques becomes more evident as they allow standoff measurement on a moving frame. Nevertheless when LDV is employed due to the relative in-plane motion between the LDV and the target speckle noise is generated which degrades the signal quality and makes this application not very straightforward but challenging. One of the first Laser Doppler Vibrometer on moving frame is adopted to measure and monitor the ground vibration, aiming at detection of buried land mines. The major addressed difficulty in this application is the speckle noise present in the acquired signal. In general the signal quality and the Signal to Noise Ratio (SNR) are a function of the laser spot size and wave length, measurement distance, relative velocity and sampling frequency. A trade-off between these factors, which are not always intuitive would help to minimize the noise floor due to the speckle noise. In this paper a test rig is presented which allows to study the speckle noise at different measurement ranges, between 1.8 and 2.8 m, and different velocities, up to 150 km/h. The results might serve as a guideline to the design process of a LDVMF.

Rahimi, Siamand; Li, Zili; Dollevoet, Rolf

2014-05-01

70

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

71

Laser doppler techniques for sizing particulate pollutants and therapeutic aerosols  

Science.gov (United States)

A particle size analyzer based on laser Doppler velocimetry has been developed for measuring, in real time, the aerodynamic size distribution of aerosol particulates in the respirable range 0.1 to 10.0 ?m in diameter. The instrument, a single particle aerodynamic relaxation time analyzer, measures the aerodynamic relaxation time of individual suspended particles and droplets without removing the particulates from their aerosol phase. Measurements can be made at a maximum count rate of 200 particles/sec, although coincidence error restricts the count rate to a lower limit. The size resolution is within +/-5% of the measured aerodynamic diameter. Currently, three prototype SPART analyzers are being used for: (1) studying aerodynamic size distribution and lung retention of therapeutic aerosols, (2) measuring fractional efficiency of electrostatic precipitators as a function of size and electrical resistivity of flyash particles, and (3) characterizing atmospheric and household aerosols.

Mazumder, M. K.; Hiller, F. C.; Ware, R. E.; Wilson, J. D.; McLeod, P. C.

1980-12-01

72

Velocity bias in two component individual realization laser Doppler velocimetry  

International Nuclear Information System (INIS)

In addition to the typical biasing problems associated with one component Laser Doppler Velocimetry (LDV), two component LDV measurements can suffer from other types of bias. In particular, coincidence bias is of interest. This type of velocity bias results from requiring simultaneous, or nearly simultaneous, measurements of the velocity components. In this study, two velocity bias correction schemes, based on the time between velocity samples, together with three different approaches for constant time-interval sampling of the velocity data have been evaluated. The effects of coincidence seeding rate and coincidence time window on velocity, normal, and Reynold's stress measurements are presented. Measurements with narrow coincidence window settings and/or low coincidence seeding rate resulted in velocity measurements which were larger than the true local average

1986-01-01

73

[Determining burn depth: clinical assessment and laser Doppler imaging].  

Science.gov (United States)

Early accurate determination of burn depth is important to determine the optimal treatment of burns. The method most used to determine burn depth is clinical assessment. This is a cheap method, 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. It is hypothesised that the introduction of LDI will lead to quicker decisions as to whether or not to operate, possibly leading to a shorter length of hospital stay and lower medical costs. To test this hypothesis, a multicentre randomized controlled trial is presently being conducted in the Dutch burn centres. PMID:22853769

Hop, M Jenda; van Baar, Margriet E; Nieuwenhuis, Marianne K; Dokter, Jan; Middelkoop, Esther; van der Vlies, C H Kees

2012-01-01

74

Model-based quantitative laser Doppler flowmetry in skin  

Science.gov (United States)

Laser Doppler flowmetry (LDF) can be used for assessing the microcirculatory perfusion. However, conventional LDF (cLDF) gives only a relative perfusion estimate for an unknown measurement volume, with no information about the blood flow speed distribution. To overcome these limitations, a model-based analysis method for quantitative LDF (qLDF) is proposed. The method uses inverse Monte Carlo technique with an adaptive three-layer skin model. By analyzing the optimal model where measured and simulated LDF spectra detected at two different source-detector separations match, the absolute microcirculatory perfusion for a specified speed region in a predefined volume is determined. qLDF displayed errors perfusion increase with qLDF than cLDF, due to nonlinear effects in the latter. The qLDF showed that the perfusion increase occurred due to an increased amount of red blood cells with a speed >1 mm/s.

Fredriksson, Ingemar; Larsson, Marcus; Strömberg, Tomas

2010-09-01

75

Absolute flow velocity components in laser Doppler flowmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method to separate a Doppler power spectrum into a number of flow velocity components, measured in absolute units (mm/s), is presented. A Monte Carlo software was developed to track each individual Doppler shift, to determine the probability, p(n), for a photon to undergo n Doppler shifts. Given this shift distribution, a mathematical relationship was developed and used to calculate a Doppler power spectrum originating from a certain combination of velocity components. The non linear Levenb...

2006-01-01

76

Frequency-domain, wide-field laser Doppler in vivo imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne optical-mixing configuration, that can create wide-field laser Doppler maps. As an illustration, we show results obtained in a mouse brain, in vivo, showing the Doppler signature of blood flow. The instrument is based on the frequency-shifting digital holography scheme.

Atlan, Michael; Gross, Michel; Forget, Benoit; Vitalis, Tania; Rancillac, Armelle; Dunn, Andrew

2006-01-01

77

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 techniques

2007-01-01

78

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

79

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

2011-11-01

80

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

 
 
 
 
81

Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow  

Directory of Open Access Journals (Sweden)

Full Text Available Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6 exists a small, or negligible pipe wall influence on laser- -Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analyzed and determined for used test rig and for some other pipe geometries. [Projekat Ministarstva nauke Republike Srbije, br. TR 35046

Risti? Slavica S.

2012-01-01

82

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

1993-01-01

83

Sub-Doppler Laser Cooling of Thulium Atoms in a Magneto-optical Trap  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have experimentally studied sub-Doppler laser cooling in a magneto-optical trap for thulium atoms working at the wavelength of 410.6\\,nm. Without any dedicated molasses period of sub-Doppler cooling, the cloud of $3\\times 10^6$ atoms at the temperature of 25(5)\\,$\\mu$K was observed. The measured temperature is significantly lower than the Doppler limit of 240$\\mu$K for the cooling transition at 410.6\\,nm. High efficiency of the sub-Doppler cooling process is due to a near...

Sukachev, D.; Sokolov, A.; Chebakov, K.; Akimov, A.; Kanorsky, S.; Kolachevsky, N.; Sorokin, V.

2010-01-01

84

Vortex generating mass flowmeter  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a vortex generating flowmeter. It comprises: a first port; a second port; a flow measurement passage between the ports; a restriction formed in the flow passage between the first and second ports, the restriction comprising a converging diverging nozzle; a rod producing drag in the passage between the restriction and the second port; and means for sensing fluid pressure in the vicinity if the rod.

Hughes, N.

1990-01-30

85

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

86

Optical design for laser Doppler angular encoder with sub-nanoradian sensitivity  

Energy Technology Data Exchange (ETDEWEB)

A novel laser angular encoder system has been developed based on the principles of radar, the Doppler effect, optical heterodyning, and self aligning multiple reflection optics. Using this novel three dimensional multiple reflection optical path, a 10 to 20 times better resolution has been reached compared to commercially available laser Doppler displacement meters or laser interferometer systems. With the new angular encoder, sub-nanoradian resolution has been attained in the 8 degree measuring range in a compact setup about 60 mm (H) x 150 mm (W) x 370 mm (L) in size for high energy resolution applications at the Advanced Photon Source undulator beamline 3-ID.

Shu, D.; Alp, E.E.; Barraza, J.; Kuzay, T.M.; Mooney, T.

1997-09-01

87

Enhanced Doppler ultrasound imaging of interstitial laser therapy in rat mammary tumors  

Science.gov (United States)

In order to better develop ultrasonography for use in monitoring interstitial laser therapy (ILT), we imaged rat mammary tumors using power Doppler ultrasound in conduction with intravenous contrast agent (Albunex) before and after laser therapy. Small vessel perfusion throughout a variable portion of the tumor could be detected by power Doppler ultrasound. Lesions created with diode laser by delivery of 500 to 3000 J appeared as perfusion defects on post-treatment images. Image topography and lesion size correlated with gross histologic findings. We conclude that ultrasonographic monitoring of local changes in blood flow using contrast enhancing agent can be useful in characterizing lesions created with ILT.

Zasuly, James M.; Fan, Ming; Dowlatshahi, Kambiz

1997-05-01

88

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

89

Insensitivity of single particle time domain measurements to laser velocimeter 'Doppler ambiguity.'  

Science.gov (United States)

It is shown that single particle time domain measurements in high speed gas flows obtained by a laser velocimeter technique developed for use in wind tunnels are not affected by the so-called 'Doppler ambiguity.' A comparison of hot-wire anemometer and laser velocimeter measurements taken under similar flow conditions is used for the demonstration.

Johnson, D. A.

1973-01-01

90

Doppler-limited dye laser excitation spectroscopy of HCCl  

Science.gov (United States)

The cw dye laser excitation spectrum of the Ã1A?(050) ? X˜1A'(000) vibronic band of HCCl was observed between 16 539 and 16 656 cm -1 with the Doppler-limited resolution, 0.03 cm -1. The HCCl molecule was generated by the reaction of discharged CF 4 with CH 3Cl. The observed spectra were assigned to c-type transitions with ? Ka = ±1 and also to axis-switching transitions with ? Ka = 0 or -2, but all with K' a = 0, both for HC 35Cl and HC 37Cl. A rotational analysis yielded the rotational constants and quartic centrifugal distortion constants for the ground vibronic state and the band origin. A weak vibronic band, about one-third as intense as the main band, was found at about 57 cm -1 to the violet of the main band for both isotopic species, and was ascribed to a transition from the ground vibronic state to a vibrational level, possibly (041), of the à state. The rotational levels of HC 35Cl in the à state showed a large perturbation; the J' = 8, 9, and 10 levels were found to be split into two components. A normal coordinate analysis was carried out to calculate the centrifugal distortion constants and the inertia defect, which were in fair agreement with the observed values. The molecular structure of HCCl in the ground vibronic state was recalculated from the rotational constants of the two isotopic species combined with the 0.75 B0 + 0.25 C0 value previously reported for DC 35Cl.

Kakimoto, Masao; Saito, Shuji; Hirota, Eizi

1983-01-01

91

Soap film gas flowmeter  

International Nuclear Information System (INIS)

A soap film gas flowmeter is described comprising: a flow tube having a hollow body with opposite open ends through which a soap film is propelled and a first closed chamber housing a soap solution. It also includes means for supporting the flow tube in a substantially vertical position with the open bottom end of the flow tube disposed in the first chamber above the soap solution; a second closed chamber into which the open top end of the flow tube extends and gas inlet means for introducing gas into the first chamber at a flow rate to be measured using the flowmeters. A gas exit means is included for discharging the gas introduced into the first chamber through the second chamber. Plus there are means for generating a single soap bubble from the soap solution substantially at the bottom end of the flow tube and a relatively large opening in the flowtube for providing an open passageway for inlet gas to pass through the flowtube when the bottom open end of the flowtube is covered by the soap solution

1987-01-01

92

Signal parameters estimation using time-frequency representation for laser doppler anemometry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes a processing method to estimate parameters of chirp signals for Laser Doppler Anemometry (LDA). The Doppler frequency as well as additional useful parameters are considered here. These parameters are the burst width and the frequency rate. Different estimators based on the spectrogram are proposed. Cramer-Rao bounds are given and performance of the estimators compared to the state of the art using Monte-Carlo simulations for synthesized LDA signals. The characteristics of...

Baral-baron, Gre?gory; Lahalle, Elisabeth; Fleury, Gilles; Lacondemine, Xavier; Schlotterbeck, Jean-pierre

2012-01-01

93

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

Science.gov (United States)

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; Alexandre, Daniel; Gross, Michel

2014-04-01

94

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

Science.gov (United States)

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. PMID:24787825

Verrier, Nicolas; Alexandre, Daniel; Gross, Michel

2014-04-21

95

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

96

Proving Coriolis flowmeters  

Energy Technology Data Exchange (ETDEWEB)

Coriolis meters provide significant advantages for custody transfer measurement of fluids. The most obvious feature is the Coriolis meter`s ability to provide a direct mass flow measurement. This makes Coriolis meters ideally suited to measuring products which are commonly accounted for on a mass basis, such as LPG, NGL, ethylene, liquid CO{sub 2}. Using a single Coriolis meter simplifies the metering system by replacing a volumetric flowmeter, densitometer, and flow computer, with a single measurement device. Another unique feature of Coriolis meters is their ability to measure fluid density independently of mass flow rate. The density measurement is determined in the same manner as any vibrating tube densitometer. By measuring both the mass flow rate ({center_dot}m) and density ({rho}), the Coriolis meter can provide a volumetric flow measurement (q) by performing the following calculation: q = {center_dot}m / {rho}. Coriolis meters have no rotating parts such as bearings or gears, that wear with time. This reduces maintenance costs. Since solids can flow through the meters without damage, strainers are generally unnecessary. Also, gas or vapor in the process fluid which can damage turbine meters due to overspin, will not harm Coriolis meters. The measurement accuracy of Coriolis meters, {+-}0.15%, is suitable for custody transfer measurement. The meters are capable of measuring flow bi-directionally. This is particularly advantageous for loading rack and cavern storage applications. Flowmeters which are used for custody transfer measurement, generally require some means to prove meter accuracy. The principles of operation of Coriolis meters are fundamentally different than those of turbine or positive displacement meters. In order to properly prove these meters it is important to understand some basics about the meters operation and output signals.

Apple, C. [Micro Motion, Inc., Houston, TX (United States)

1995-12-01

97

Two-beam nonlinear Kerr effect to stabilize laser frequency with sub-Doppler resolution  

CERN Document Server

Avoiding laser frequency drifts is a key issue in many atomic physics experiments. Several techniques have been developed to lock the laser frequency using sub-Doppler dispersive atomic lineshapes as error signals in a feedback loop. We propose here a two-beam technique that uses non-linear properties of an atomic vapor around sharp resonances to produce sub-Doppler dispersive-like lineshapes that can be used as error signals. Our simple and robust technique has the advantage of not needing either modulation or magnetic fields.

Martins, Weliton Soares; de Silans, Thierry Passerat; Oriá, Marcos; Chevrollier, Martine; 10.1364/AO.51.005080

2012-01-01

98

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.

2012-02-01

99

Two-beam nonlinear Kerr effect to stabilize laser frequency with sub-Doppler resolution.  

Science.gov (United States)

Avoiding laser frequency drifts is a key issue in many atomic physics experiments. Several techniques have been developed to lock the laser frequency using sub-Doppler dispersive atomic lineshapes as error signals in a feedback loop. We propose here a two-beam technique that uses nonlinear properties of an atomic vapor around sharp resonances to produce sub-Doppler dispersivelike lineshapes that can be used as error signals. Our simple and robust technique has the advantage of not needing either modulation or magnetic fields. PMID:22858948

Martins, Weliton Soares; Cavalcante, Hugo L D de S; Passerat de Silans, Thierry; Oriá, Marcos; Chevrollier, Martine

2012-07-20

100

Signal processing of laser-Doppler vibrometer output for mine detection  

Science.gov (United States)

Sound waves from a powerful loudspeaker can excite a certain type of vibration of the surface of the ground when a mine is present and near the surface. In turn, a laser-Doppler vibrometer can be employed to acquire information about the surface vibrations. In particular, the portion of the ground surface that is vibrating has the shape of the projection of the mine onto the surface. This paper discusses a method based on Bayesian probability theory for processing laser- Doppler vibrometer data to infer the periphery of any surface vibration pattern. Difficulties with using a phase- lock loop in determining a surface map are also discussed.

Goggans, Paul M.; Smith, Charles R.

1999-08-01

 
 
 
 
101

Isotope shifts of Er I measured by diode-laser-based doppler-free spectroscopy  

International Nuclear Information System (INIS)

High-resolution sub-Doppler spectra of Er I were measured in some transition Lines using saturation absorption spectroscopy. Er atomic sample was prepared by a sputtering technique employing an Er-Ar hollow-cathode discharge lamp. For an atomic excitation laser, we used a single-mode tunable diode laser with an external cavity. As a result, sub-Doppler spectra for four transitions, which have wavelengths between 630 and 690 nm, were obtained. Analyzing the spectra, we obtained the isotope shifts ??(Er170 - Er168) and ??((Er168 -Er166) with an accuracy of 4 MHz

2000-11-03

102

Sub-Doppler Laser Cooling of Thulium Atoms in a Magneto-optical Trap  

CERN Multimedia

We have experimentally studied sub-Doppler laser cooling in a magneto-optical trap for thulium atoms working at the wavelength of 410.6\\,nm. Without any dedicated molasses period of sub-Doppler cooling, the cloud of $3\\times 10^6$ atoms at the temperature of 25(5)\\,$\\mu$K was observed. The measured temperature is significantly lower than the Doppler limit of 240$\\mu$K for the cooling transition at 410.6\\,nm. High efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Land\\'e-$g$ factors of the lower $4f^{13}6s^{2}\\, (J\\,=\\,{7}/{2})$ and the upper $4f^{12}5d_{3/2}6s^{2}\\, (J\\,=\\,{9}/{2})$ cooling levels.}

Sukachev, D; Chebakov, K; Akimov, A; Kanorsky, S; Kolachevsky, N; Sorokin, V

2010-01-01

103

Study on simulation and experiment of laser micro-Doppler effect for detecting complex vibration  

Science.gov (United States)

The spectrum of radar signal will be modulated by moving target or vibration and turning part of the target, this is called micro-Doppler effect. It is a new way of using micro-Doppler effect to realize the feature extraction and target recognition. Because the complex vibration target has more complicated frequency component than the single frequency target, so it is very useful to do the research of simulation and experiment of laser micro-Doppler effect for detecting complex vibration. In this paper, the research on simulation and experiment of laser micro-Doppler effect for detecting complex vibration of moving target was developed based on the simulation research of micro-Doppler effect in lidar. Firstly, the geometry of complex vibrating target detection in radar was established. Secondly, the simulation and experiment signal sources were compared and also the returned signals in radar of the simulation and experiment were compared, the compared results showed that the two complex signal sources were very similar, and the frequency change trend of returned signals in radar was the same. Thirdly, joint time-frequency analysis method of the reassigned smoothed pseudo Wigner-Ville distribution (RSPWVD) was introduced to analyze the signals. The results showed that in RSPWVD, the waveform of the vibration target, the target vibration period, the Doppler frequency shift and the target's speed can be got. The simulation results and the experiment results got by the RSPWVD had the basically same frequency characteristics. So the RSPWVD can reflect very well the micro-Doppler characteristics of moving target's complex vibration. In conclusion it proved the validity of the simulated model, also it proved that using this time-frequency method to analyze the micro-Doppler signal of complex vibration was correct. And it laid the foundation of further using lidar to realize the classification and identification of target.

Yuan, Shuai; Zhang, Juan; Liu, Mei-juan; Zhang, Jun

2013-08-01

104

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.)

1980-01-01

105

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

International Nuclear Information System (INIS)

Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S1/2?5P3/2?6S1/2?nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth 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.

2011-11-01

106

Influence of Doppler broadening on the stability of monomode ring lasers  

Energy Technology Data Exchange (ETDEWEB)

A single running mode in a ring gas laser where inhomogeneous Doppler broadening is dominant is considered. The analytic linear stability analysis of the stationary solution leads to the conclusion that in the bad cavity limit a second threshold exists. A salient property is that it occurs at low intensity in contradistinction to homogeneously broadened media where it occurs at high intensity.

Mandel, P.

1983-02-15

107

Precise micro flow rate measurements by a laser Doppler velocity profile sensor with time division multiplexing  

International Nuclear Information System (INIS)

This paper presents the measurement of flow rate inside a microchannel by using a laser Doppler technique. For this application a novel laser Doppler velocity profile sensor has been developed. Instead of parallel fringe systems, two superposed fan-like fringe systems with opposite gradients are employed to determine the velocity distribution inside the microchannel directly. The sensor utilizes the time division multiplexing technique to discriminate both fringe systems. A velocity uncertainty of 0.18% and a spatial resolution of 960 nm are demonstrated in the flow, which is the highest spatially resolved measurement by a laser Doppler technique published to date. Flow rate measurements, in the range of 30 µl min?1, with a statistical uncertainty of 5 × 10?4 are further presented. In comparison to a reference, by precise weighing, the mean deviation between both measurement principles amounts to 1%. With the advantage of high spatial resolution with simultaneous low velocity uncertainty, the laser Doppler velocity profile sensor offers a new tool for microfluidic diagnostics, e.g. in lab-on-a-chip systems or for drug delivery, which requires very small flow rates

2010-07-01

108

Spectral analysis of the signal from the Laser Doppler Velocimeter - Turbulent flows.  

Science.gov (United States)

A method for prediction and analysis of the spectrum of the signal from the Laser Doppler Velocimeter is presented. The results relate the heterodyne spectrum of the signal to the space-time correlation function for the turbulent transport of tracer particles in the fluid and to the characteristics of the optical system.

Edwards, R. V.; Angus, J. C.; Dunning, J. W., Jr.

1973-01-01

109

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

2007-01-01

110

Velocity measurements of sputtered particles using the Laser-Doppler method  

International Nuclear Information System (INIS)

The development of tunable single frequency dye lasers has enabled the realization of a Doppler-Shift-Laser-Spectrometer (DSLS) for the detection and energy analysis of neutral sputtered particles. It is based on the Doppler-shifted resonance excitation by monochromatic radiation. The particle beam to be measured is intersected by two laser beams at 900 and 300 respectively. The laser is turned over a resonance line of the species to be investigated. The sharp non-Doppler-shifted 900 spectrum is used as zero marking on the velocity axis. The intensity of the Doppler-shifted 300 fluorescence spectrum is directly proportional to the particle intensity in the corresponding velocity interval. A high detection sensitivity of about 50 particles/cm3 and a velocity resolution of 50 m/s can be achieved. With the DSLS it is possible to investigate one particular kind of sputtered atoms with high resolution over a wide energy region. Results for different targets bombarded with rare gas ions are presented. The obtained spectra allow to determine the influence of slow thermal processes, thermal spikes and collision cascades to the sputtering process. A comparison with results obtained with time-of-flight experiments is given. (orig.)

1980-03-01

111

Basic problems associated with the interpretation of the fluorescence spectra in Doppler-shift laser spectroscopy  

International Nuclear Information System (INIS)

The influence of power broadening and the interpretation of the measured fluorescence spectra as being proportional to the flux or density in Doppler-shift laser fluorescence spectroscopy using cw-dye laser excitation are discussed. Power broadening was found to be negligible for the measurement of energy spectra of sputtered species and in the low energy regime (below several 1000m/s) the measured fluorescence signal of Na was found to be proportional to the flux. (Author)

1982-02-13

112

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Kapralov S.V.; Shapkin Y.G.; Frolov I.A.; Afanasieva G.A.

2011-01-01

113

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)

2002-01-01

114

International Symposium on Applications of Laser-Doppler Anemometry to Fluid Mechanics, Lisbon, Portugal, July 5-7, 1982, Proceedings  

Energy Technology Data Exchange (ETDEWEB)

The papers contained in this volume provide an overview of applications of laser Doppler anemometry to fluid mechanics, with attention given to shear, internal, two-phase, isothermal, nonisothermal, and separated flows. The discussion also covers fiber optics, rod bundles, signal processing, and rotating machinery. Papers are presented on coherent structures in axisymmetric jets, two-dimensional laser Doppler anemometer measurements, a compact pulsed LDA for airborne and wind-tunnel applications, and laser velocimeter measurements in separated flows with combustion.

1982-01-01

115

Electro-magnetic flowmeters  

International Nuclear Information System (INIS)

Full details of the invention are given. A sensing unit assembly for an electromagnetic flux distortion flowmeter for use in liquid metal coolant of a nuclear reactor is described. The assembly comprises coils of electrically insulated conductors each wound on an individual former. The formers and coils are mounted coaxially on a spine to form at least three spaced groups arranged end to end. Each group comprises two secondary coils and an intermediate primary coil. Leads extend along a duct formed in the spine, each lead terminating at a common end. Alternative versions of the assembly are also described. The primary coil leads are connected to an alternating power supply; those for the secondary coils connected to suitable display instrumentation. When liquid metal flows along the conductor the electromagnetic field is disturbed and the induced voltage in the secondary coils is disturbed-(set at zero for no flow); the distortion depends on the rate of flow. When the induced voltage differential of at least two of the groups falls or rises outside a pre-set level a trip signal is initiated to shut down the reactor. (UK)

1980-01-01

116

Pulsed laser Doppler flowmetry for increased signal-to-noise ratio and probed depth  

Science.gov (United States)

In laser Doppler flowmetry (LDF) deep perfusion measurements can be realized by using a large separation between the fibers used for illumination and detection. In order to achieve a sufficient signal-to-noise ratio, the power of the laser light can be increased, but only to the limit indicated by the safety regulations. In this paper, pulsed laser Doppler flowmetry (pLDF) is presented as a manner to increase the SNR without exceeding the safety limits. The method is based on the principle that light is needed only when the signal is being sampled. The setup is presented, and we will show results that indicate that equivalent results are obtained for a pulsed and continuous wave setup (cwLDF), however with a much smaller tissue exposure. Furthermore, the limits encountered in realizing a pulsed system will be discussed.

Steenbergen, Wiendelt; Kolkman, Roy G. M.; Woldberg, Sven; de Mul, Frits F. M.

2003-07-01

117

Laser-induced fluorescence and Doppler-free polarization spectra in a low density hydrogen plasma  

International Nuclear Information System (INIS)

The H? spectral line profile in a low-density hydrogen plasma of a microwave discharge has been measured by the laser-induced fluorescence and the Doppler-free polarization spectroscopy methods with a pulsed high-power tunable laser. The saturation characteristics of the output signals in each method were examined in detail with observations of typical saturation broadening. The original homogeneous width of the line was estimated in the limit of no laser pumping, and various factors governing this width are discussed while demonstrating the importance of the clarification of molecular processes in the discharge. In the Doppler-free spectra a large distortion of the spectrum was also found under different operating conditions; it was attributed to the plasma opacity effect. (author)

1987-01-01

118

Sub-Doppler Laser Cooling With Planar-Geometry Optics And a Single Laser Beam  

Science.gov (United States)

We have realized a new magneto-optical trap geometry using a single laser beam incident on planar optics. In this arrangement we trap 10^6 ^87Rb atoms and have achieved temperatures of 40 ?K. We have been inspired by the continued interest in miniaturizing the technology for ultra-cold atomic physics, particularly for applications concerning sensing. Work towards the achievement of small scale, all-integrated magneto-optical traps (MOT) has been very active, such as the realization of MOTs in a microfabricated pyramidal structure. Here we present an new design with significant advantages as a compact source of cold atoms. A triplet of diffraction gratings splits a laser beam such that four beams cross a tetrahedral configuration in the MOT region. This arrangement offers a uniformly balanced radiation pressure area, and becomes suitable for efficient sub-Doppler cooling. The planar configuration offers maximal optical access to the atomic cloud and can be easily turned into an integrated micro-trap, benefiting from standard lithography processes. In addition, a micro-fabricated tetrahedral configuration offers an ideal tool for a high phase stability optical lattice, with the benefit of fixed lattice geometry.

Griffin, Paul; Vangeleyn, Matthieu; Riis, Erling; Arnold, Aidan

2011-06-01

119

Laser-tissue interaction with fs pulses: measurement of the recoil momentum by laser Doppler vibrometry  

Science.gov (United States)

Currently ultra short pulses with pluse duration close to 100 fs are investigated for tissue ablation to perform laser surgery in a microscopic scale without any damage to the remaining tissue. Several groups showed already that the risk of thermal damage can be avoided; however the ablated material leaves the surface with a high velocity which leads to significant recoil momentum to the tissue. This paper focuses on the experimental set-up to measure this momentum transfer. Various set-ups had been developd over the last years like a pendulum that is highly senstive but cannot ensure that in a train of pulses each pulse will impact at exactly the same spot. A sliding rod in a glass tube ensured the constant impact point but is sensitive to several environmental conditions, which are hard to control. Recently, special swing plates were designed as vibration disks. The small sample was mounted in the center of this plate and exposed by fs pulses of a TiSa laser. The beam of a laser Doppler vibrometer was focused onto the backside of the plate monitored its motion. This set-up enabled us to measure the recoil momentum. While the total momentum transfer could be well determined to ?p=6 10-3 g mm/s, the question about a mechanical damage, for example for hair cells in the inner ear is much more difficult to answer, since this depends on the time in which the ablated materials leaves the surface. Evaporation times of 40 ps would lead to serious risk ofhar cell damage.

Sessa, Gaetano; Travaglini, Michele; Mittnacht, Dirk; Foth, Hans-Jochen

2003-07-01

120

Vibration measurements on rotating machinery using laser Doppler velocimetry  

Science.gov (United States)

This paper explores the use of laser vibrometry for vibration measurement directly from a rotating component. The presence of a surface velocity component due to the rotation itself is shown to create a strong measurement dependency on vibration perpendicular to the intended measurement direction. Particular ambiguity results at synchronous frequencies. A mathematical means to resolve the genuine vibration components from two simultaneous laser vibrometer measurements is presented and shown to be effective in the study of nonsynchronous rotor vibrations.

Rothberg, S. J.; Halliwell, N. A.

1994-07-01

 
 
 
 
121

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

122

Development and testing of laser Doppler system components for wake vortex monitoring. Volume 2: Scanner operations manual  

Science.gov (United States)

The theory and operation of the scanner portion of the laser Doppler system for detecting and monitoring aircraft trailing vortices in an airport environment are discussed. Schematics, wiring diagrams, component values, and operation and checkout procedures are included.

Edwards, B. B.; Coffey, E. W.

1974-01-01

123

Exploiting continuous scanning laser Doppler vibrometry (CSLDV) in time domain correlation methods for noise source identification  

Science.gov (United States)

This paper proposes the use of continuous scanning laser Doppler vibrometry (CSLDV) in time domain correlation techniques that aim at characterizing the structure-borne contributions of the noise emission of a mechanical system. The time domain correlation technique presented in this paper is based on the use of FIR (finite impulse response) filters obtained from the vibro-acoustic transfer matrix when vibration data are collected by laser Doppler vibrometry (LDV) exploited in continuous scan mode (CSLDV). The advantages, especially in terms of source decorrelation capabilities, related to the use of CSLDV for such purpose, with respect to standard discrete scan (SLDV), are discussed throughout the paper. To validate this approach, vibro-acoustic measurements were performed on a planetary gear motor for home appliances. The analysis of results is also supported by a simulation.

Chiariotti, Paolo; Martarelli, Milena; Revel, Gian Marco

2014-07-01

124

Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms  

CERN Multimedia

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. The Doppler limit heating rate due to radiative collisions is calculated for Mg-24 atoms in a magneto-optical trap based on the singlet S_0 - singlet P_1 atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We also describe a channelling mechanism due to the missing Q branch in the excitation scheme, which could lead to a suppression of inelastic collisions, and find that this mechanism is not present in our simulation results due to the multistate character of the excitation process.

Piilo, J; Suominen, K A

2003-01-01

125

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

126

Blood flow velocity imaging of malignant melanoma by micro multipoint laser Doppler velocimetry  

Science.gov (United States)

We have developed a laser Doppler velocimeter to measure blood flow, the micromultipoint laser Doppler velocimeter (?-MLDV). This equipment can measure absolute velocity and, based on this, can display the course of blood vessels. In this study, we attempted to perform blood flow velocity imaging of malignant melanoma transplanted to the mouse ear. We found that blood flow velocity of the formed blood vessels originating in the melanoma was much greater than that of the capillary vessels in normal skin. Furthermore, the form of the tumor was clearly visible from the blood flow velocity image. These experimental results suggest that ?-MLDV has potential as a diagnostic method for distinguishing benign nevi from malignant melanomas.

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

2010-09-01

127

Scanning laser Doppler is a useful technique to assess foot cutaneous perfusion during femoral artery cannulation.  

Science.gov (United States)

BACKGROUND: Measurement of cardiac output and extravascular lung water in critically ill patients using femoral artery double-indicator dilution involves femoral artery catheterization. The potential risk of vascular compromise to the limb may be exacerbated in patients receiving vasopressors. The utility of scanning laser Doppler flowmetry to measure changes in pedal perfusion following catheterization was assessed. RESULTS: There were no significant changes in mean occlusion pressures or in cutaneous perfusion between either leg or between measurement time points, immediately after or 24 h following insertion of the catheters. CONCLUSIONS: Scanning laser Doppler flowmetry is easily used to assess changes in foot perfusion and the effect of interventions that may reduce blood flow to the skin of the foot. Femoral artery catheterization for double-indicator dilution measurements does not reduce calf occlusion pressures or foot skin perfusion in patients receiving vasopressor drugs. PMID:11056731

Boyle; Roberts; Ng; Berkenstadt; McLuckie; Beale; Mason

1999-01-01

128

Analysis of complex three-dimensional flows by laser Doppler velocimetry - Data processing and display  

Science.gov (United States)

This paper presents a review of experimental studies performed at the Aerodynamics Department of ONERA on three-dimensional separation both in incompressible and compressible flows. These studies call upon an intensive use of Laser Doppler Velocimetry as a mean to explore complex flows including separated regions, strong vortical structures, high velocity fluctuations and shock-waves. Special effort has been made to arrive at a clear understanding of the flowfield organization by the use of modern processing techniques including color display.

Chanetz, B.; Molton, P.; Pagan, D.; Pot, T.

129

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

1991-06-23

130

Microregional blood flow in murine and human tumours assessed using laser Doppler microprobes.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A multichannel laser Doppler system has been used to measure microregional fluctuations in perfusion in the HT29 human tumour xenograft and in patients with advanced malignant disease. A comparison is made with previously obtained data for the SaF, a transplantable murine tumour. The 300 microns diameter probes recorded fluctuations in erythrocyte flux in tumour microregions with an estimated volume of 10(-2) mm3. Of the 66 human tumour microregions sampled, 26% showed a change in erythrocyte...

Hill, S. A.; Pigott, K. H.; Saunders, M. I.; Powell, M. E.; Arnold, S.; Obeid, A.; Ward, G.; Leahy, M.; Hoskin, P. J.; Chaplin, D. J.

1996-01-01

131

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

132

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Jenda, Hop M.; Hiddingh Jakob; Stekelenburg Carlijn; Kuipers Hester C; Middelkoop Esther; Nieuwenhuis Marianne K; Polinder Suzanne; van Baar Margriet E

2013-01-01

133

Instantaneous measurement of magnetic field strength with combining beam probe and Doppler-tuned laser spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

A novel technique to measure the magnetic field strength is demonstrated, which is based on blow-off beam probing combined with Doppler-tuned laser spectroscopy. The field strength is determined from the Zeeman splitting of the LiI resonance line (670.8 nm) with good time and spatial resolutions (..delta..t<100 ..mu..s, ..delta..r<5 mm). The measurable field strength is less than 1 T with an accuracy of 10%.

Yamaoka, H.; Kadota, K.; Yamai, H.; Kano, S.S.; Fujita, J.

1988-01-01

134

Determination of air and hydrofoil pressure coefficient by laser doppler anemometry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Compari...

2010-01-01

135

Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical traps  

CERN Multimedia

Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit population-wide sub-Doppler cooling due to their near degeneracy of excited and ground state Lande g factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Doppler-cooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degen...

Youn, Seo Ho; Lev, Benjamin L

2010-01-01

136

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

137

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

1987-04-15

138

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

139

Facts and fallacies of vortex flowmeters  

Energy Technology Data Exchange (ETDEWEB)

Vortex flowmeters have been popular since the late 1960s. They have been sold as everything from a panacea for severe service flow applications to a direct replacement for orifice meters. In many ways, vortex flowmeters have not lived up to industry expectations and therefore, have obtained a bad reputation. However, vortex flowmeters can be good flow measurement devices if applied properly, and they do have a place in the processing industries for certain flow applications.

DeVries, E.A.

1982-08-01

140

Laser Doppler measurement of relative blood velocity in the human optic nerve head  

Energy Technology Data Exchange (ETDEWEB)

The Doppler shift frequency spectrum (DSFS) of laser light scattered from red blood cells (RBCs) moving in the microcirculation of the optic nerve head has been recorded in normal volunteers by means of a fundus camera laser Doppler velocimeter. The width of the DSFS, which varies in proportion to the speed of the RBCs, has been characterized by a parameter alpha. With the use of a model for the scattering of light by tissue and RBCs and for the RBC velocity distribution, values of alpha recorded at normal intraocular pressure (IOP) suggest that the RBCs that contribute to the Doppler signal are flowing in capillaries. The parameter alpha was found to vary markedly with the IOP and with the phase of the ocular pressure pulse at elevated IOP. The return of the speed of RBCs toward normal, which is observed after a step increase of IOP above normal and after a step decrease below normal, has been attributed to an autoregulatory response of the optic nerve circulation.

Riva, C.E.; Grunwald, J.E.; Sinclair, S.H.

1982-02-01

 
 
 
 
141

[Doppler effect on width of characteristic line in plasma induced by pulsed laser ablating Al].  

Science.gov (United States)

Aluminum (Al) plasma was induced with a pulsed Nd: YAG laser beam ablating Al target in Ar. Time-resolved information of the plasma radiation was taken with time-resolved technique, and the spectra of the radiation were recorded with an optical multi-path analyzer (OMA III ), whereupon, time-resolved spectra of the plasma radiation induced by pulsed laser were acquired. Based on the experiment data, Al resonant double lines, Al I 396.15 nm, Al I 394.40 nm, were respectively fitted with Lorentz, Gauss and their linear integrated function (abbr. Integrated function), whereupon, Lorentz and Gauss elements were separated from the experiment data profile curve. By contrasting Lorentz with Gauss curve separated, it was found that the experiment curve mainly consisted of Lorentz element, a with little Gauss. By contrasting Lorentz with Integrated fitting curve for experiment data, a visual picture of the characteristic lines broadened by Doppler effect was exhibited. According to the visual picture, the increase of full half-high width of the characteristic line broadened by Doppler effect was estimated. It was about 2 x 10(-)3 -8 x 10(-3) nm, approximating the theoretical value 6.7 x 10(-)3 nm. As a result, Doppler effect on the width of characteristic lines in the plasma could be reasonably explained by curve fitting analysis and theoretical calculation. PMID:16128055

Song, Yi-Zhong; He, An-Zhi

2005-05-01

142

Laser doppler semiconductor anemometry of vortes flow behind the vane wheel rotor of the water turbine  

DEFF Research Database (Denmark)

For hydrodynamic examinations of the turbid three-phase streams with air bubbles and with a depth more than 500 mm for the first time it is developed 2D Laser Doppler Semiconductor Anemometer LADO5-LMZ. Anemometer signal processor base on > and new procedure of adaptive selection of Doppler frequency. Complex testing of method and measuring tools have been done. Outcomes of full-scale experiments on diagnostic of nonstationary flow behind the vane wheel rotor in draught tube of the Frensis water turbine are presented from optimum regimes of activity to forced. Water discharge which has been calculated from water turbine universal performance model and calculated by measuring axial velocity profiles was compared. It is shown that the maximum aggregate error of definition of the consumption does not exceed 5%.

Meledin, V.; Anikin, Yu.

2006-01-01

143

Assessment of ocular hemodynamics after laser in situ keratomileusis using color Doppler imaging.  

Science.gov (United States)

To investigate ocular blood flow changes in healthy myopic patients following laser in situ keratomileusis (LASIK) using color Doppler imaging. Sixteen eyes of 16 myopic patients were studied. LASIK was performed and intraocular pressure was raised to levels ?65 mmHg. Color Doppler images were obtained to study the ophthalmic and central retinal arteries preoperatively and postoperatively at 1 day, 1 week, and 1 month. There was no significant correlation between patient age and preoperative ocular blood flow parameters. A significant positive correlation between the degree of myopia and the peak systolic volume of the ophthalmic artery (r = 0.6, P = 0.01) was found. A highly significant decrease in the peak systolic volume and end-diastolic volume with an increase in the resistive index of both arteries (P LASIK. LASIK is an increasingly common lifestyle procedure and further studies on larger groups are still recommended. PMID:23743872

Abou Samra, Waleed; Samera, Waleed Abu; Shahin, Maha; El-Awady, Hatem; El-Rahman, Ashraf Abd; El-Toukhy, Nahed

2014-04-01

144

Development of a quasi-continuous laser Doppler measurement method to identify structural dynamics parameters; Entwicklung einer quasi-kontinuierlichen Laser Doppler Messmethode zur Identifikation strukturdynamischer Parameter  

Energy Technology Data Exchange (ETDEWEB)

Vibration tests are performed since a long time to identify the structural parameters of aerospace structures. Usually the responses are measured by means of acceleration transducers. But meanwhile optical measurement methods are possible as well. New possibilities of experimental modal analysis arise due to the non-contacting recording of dynamic responses. In the present work the method of a continuously scanning laser Doppler Vibrometer is addressed and new measurement methods are developed. It is shown how structures can be scanned using one or two dimensional scan paths. For that purpose scan algorithms are used with constant and time varying scan frequencies and amplitudes. Moreover an adapting algorithm is developed to improve the scan procedure by adapting the scan path to the selected mode shape. The developed methods are demonstrated on an undamaged and a delaminated aluminum sandwich plate. Comparative measurements using accelerometers and digital shearography serve to evaluate the methods in practical environment. Based on the results specific properties and potential application areas of the different scan methods are derived and discussed. (orig.) [German] Versuche zur strukturdynamischen Identifikation werden bereits seit langem routinemaessig an verschiedenen Strukturen der Luft- und Raumfahrt durchgefuehrt. Dabei werden die Strukturschwingungen im Wesentlichen mit Beschleunigungsaufnehmern erfasst. Sie lassen sich seit einiger Zeit aber auch mit optischen Messmethoden aufnehmen. Aufgrund der beruehrungslosen Messung der Strukturschwingungen eroeffnen sich neue Moeglichkeiten der experimentellen Modalanalyse. In der vorliegenden Arbeit wird die Messmethode eines kontinuierlich scannenden Laser Doppler Vibrometers aufgegriffen, dargestellt und darauf aufbauend neue Messmethoden entwickelt. Es wird gezeigt, wie Strukturen ein- und zweidimensional abgescannt werden koennen. Dabei werden Scanalgorithmen mit konstanten und zeitlich veraenderlichen Scanfrequenzen und Scanamplituden eingesetzt. Zur Optimierung des Scanvorgangs wird ein Adaptionsalgorithmus entwickelt, der es ermoeglicht, den Scanweg an die jeweilige Schwingungsform anzupassen. Die Anwendung der Methoden wird an einer ungeschaedigten und einer delaminierten Aluminium Sandwichplatte demonstriert. Zur Diskussion der Praxistauglichkeit werden Vergleichmessungen mit Beschleunigungsaufnehmern sowie mit einer shearografischen Messmethode durchgefuehrt. Aus den Ergebnissen werden die spezifischen Eigenschaften sowie die geeigneten Einsatzgebiete der verschiedene Scanmethoden diskutiert und abgeleitet. (orig.)

Brehmer, A.

2003-07-01

145

Studies on the dynamics of vacuum encapsulated 2D MEMS scanners by laser Doppler vibrometry  

Science.gov (United States)

2D MEMS scanners are used for e.g. Laser projection purposes or Lidar applications. Electrostatically driven resonant torsional oscillations of both axes of the scanners lead to Lissajous trajectories for Laser beams reflected from the micro mirror. Wafer level vacuum encapsulation with tilt glass capping ensures high angular amplitudes at low driving voltages additionally preventing environmental impacts. Applying Laser Doppler Vibrometry, the effect of residual gas friction, squeezed film damping and internal friction on 2D MEMS scanners is analyzed by measuring the Q-values associated with the torsional oscillations. Vibrometry is also used to analyze the oscillatory motion of the micro mirror and the gimbal of the scanners. Excited modes of the scanner structures are identified giving rise to coupling effects influencing the scanning performance of the 2D MEMS mirrors.

Janes, Joachim; Hofmann, Ulrich

2014-03-01

146

A solid state laser system for Doppler-free spectroscopy of muonium  

International Nuclear Information System (INIS)

The thesis describes a new high precision measurement of the 1S-2S transition frequency in muonium, carried out at the ISIS facility at the Rutherford Appleton Laboratory, using a solid-state laser system. The focus of the thesis is mainly the work carried out on the pulsed part of the laser system. The transition frequency is measured by the Doppler-free spectroscopy. The two-photon 1S-2S transition is detected by observing the positive muon released after subsequent photo-ionisation from the 2S state by a third photon from the same laser field. An accurate frequency standard for the experiment was provided by a Doppler-free transition in molecular iodine. A cw Ti:sapphire laser operating around 732 nm locked to this reference transition provided a stable output for injection seeding the pulsed alexandrite laser. This has been optimised and modified to achieve a stable operation in a single transverse and longitudinal mode. There were stringent requirements on the laser pulse timing relative to an external trigger in order to synchronise the laser pulse with the muon pulse from the ISIS facility. A method of cavity length stabilisation, which reduced the jitter of the laser from approximately 20 ?s to 100ns and allowed us to trigger the laser externally, is described. This was performed in two stages using an intracavity, piezo-mounted, quartz plate and two fast, electro-optic modulators. The frequency chirp of the laser output, measured using a heterodyne technique 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. (author)

1998-01-01

147

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

1990-10-01

148

Acute radiation effects on cutaneous microvasculature: evaluation with a laser Doppler perfusion monitor  

International Nuclear Information System (INIS)

Laser Doppler perfusion monitoring is a noninvasive technique for measuring blood flow in epidermal microvasculature that makes use of the frequency shift of light reflected from red blood cells. Measurements in patients undergoing radiation therapy show increases in blood flow of ten to 25 times baseline at doses above 50 Gy, and increases are observed with doses as low as 2 Gy. Follow-up measurements show rapid decreases in flow levels after completion of therapy, but levels remain elevated even at 1 year

1988-01-01

149

Turbulence measurements in the physical model of a molten aluminum tundish using laser-Doppler velocimetry  

Science.gov (United States)

Quantitative velocity and turbulence measurements which were obtained using laser Doppler velocimetry during the course of the physical modeling of the molten aluminum flow in a tundish are presented. The experimental findings are compared to the results obtained by the computational simulation of the flow, showing favorable agreement between the two approaches. The measurements revealed asymmetric velocity and non-isotropic turbulence field near the nozzle exit. In the vicinity of the nozzle, the interaction of the impinging jet and the inclined walls gives rise to recirculating vortex structures. Downstream of the nozzle, two counter-rotating secondary cells diminish in strength.

Shen, F.; Khodadadi, J. M.; Pien, S. J.; Smith, J. T.

1993-08-01

150

[Clinic use of Laser Doppler Flowmetry (LDF) in the study of subfoveal choroidal circulation].  

Science.gov (United States)

Today our knowledge of the choroidal circulation is limited: we know its anatomy, but, on the other hand, its physiopathology remains to be fully. The choroid is involved in a number of important ocular diseases. The Laser Doppler Flowmetry (LDF) is a technique that allows non-invasive measurement of haemodynamic parameters of the subfoveal choroidal circulation. It is easy to use in daily clinic activity. The aim of this mini-review is to describe LDF studies of the choroidal circulation performed in healthy subjects under different environmental conditions, in subjects with ocular diseases, as well as studies of the effects of various drugs can induce on this circulation. PMID:21448548

Riva, C E; Falsini, B; Anselmi, G; Gari, M

2011-01-01

151

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

152

Flow rate measurement and visualization of buoyancy-driven exchange flow by laser doppler velocimeter  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation was carried out for the buoyancy-driven exchange flow in a narrow vertical pipe concerning with air ingress process during a stand pipe rupture in high temperature gas-cooled reactor. In the present study, the evaluation method of exchange flow was developed by measuring the velocity distribution in the pipe using laser Doppler velocimeter (LDV) and the flow pattern was visualized by smoke tracer method. It was found that the exchange flow fluctuated irregularly with time and space in the pipe. The velocities of the plumes obtained from visualization were almost the same as the maximum ones measured by LDV. (author).

Fumizawa, Motoo (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment)

1993-07-01

153

IN-PLANE MODAL TESTING OF A FREE ISOTROPIC PLATE USING LASER DOPPLER VIBROMETER MEASUREMENTS  

International Nuclear Information System (INIS)

In this work an experimental procedure is proposed to obtain the lowest free in-plane vibration modes of an aluminum plate. Responses are measured along two longitudinal directions on the plate surface at selected points by an out-of-plane laser Doppler vibrometer set up to measure in-plane vibrations. Excitation is made at one specific point of the plate edge using a light impact hammer. The plate is supported by silicone spheres to simulate the free edge boundary conditions and ensure a stable stationary position in order to keep the laser focus distance. Numerical finite element simulations are carried out to compute the in-plane modes and frequencies in order to compare them with the corresponding experimental results. The identified experimental modes agree very well with the numerical predictions. The smooth in-plane modes can be used to identify the plate material constitutive model parameters using existing methods proposed elsewhere by the authors.

2010-05-28

154

In-Plane Modal Testing of a Free Isotropic Plate Using Laser Doppler Vibrometer Measurements  

Science.gov (United States)

In this work an experimental procedure is proposed to obtain the lowest free in-plane vibration modes of an aluminum plate. Responses are measured along two longitudinal directions on the plate surface at selected points by an out-of-plane laser Doppler vibrometer set up to measure in-plane vibrations. Excitation is made at one specific point of the plate edge using a light impact hammer. The plate is supported by silicone spheres to simulate the free edge boundary conditions and ensure a stable stationary position in order to keep the laser focus distance. Numerical finite element simulations are carried out to compute the in-plane modes and frequencies in order to compare them with the corresponding experimental results. The identified experimental modes agree very well with the numerical predictions. The smooth in-plane modes can be used to identify the plate material constitutive model parameters using existing methods proposed elsewhere by the authors.

Batista, F. B.; Fabro, A. T.; Cóser, L. F.; Arruda, J. R. F.; Albuquerque, E. L.

2010-05-01

155

Masked velocity map imaging: a one-laser-beam Doppler-free spectroscopic technique.  

Science.gov (United States)

A novel spectroscopic technique has been developed which makes it possible to record Doppler-free resonance-enhanced multiphoton ionization (REMPI) spectra with just one laser beam. The approach simply involves masking the outer side of the phosphor screen under velocity map imaging conditions so that only those species having no velocity component parallel to the laser beam propagation direction are detected. The benefits of this method are demonstrated in spectroscopic characterization of highly translationally and rotationally excited CO fragments resulted from the 230 nm photolysis of OCS and acetone, yielding substantially improved values of the rotational constants for the B state (v'' = 0) of the CO molecule. The resolving power and the state distribution analysis of reaction products are also demonstrated for room-temperature H atoms generated by dissociation of background hydrogen molecules and oxygen atom detected from the 225.6 nm photolysis of ozone. PMID:19170563

Goncharov, Vasiliy; Herath, Nuradhika; Arregui, Andrés; Bañares, Luis; Suits, Arthur G

2009-04-23

156

In-situ position and vibration measurement of rough surfaces using laser Doppler distance sensors  

Science.gov (United States)

In-situ measurement of distances and shapes as well as dynamic deformations and vibrations of fast moving and especially rotating objects, such as gear shafts and turbine blades, is an important task at process control. We recently developed a laser Doppler distance frequency sensor, employing two superposed fan-shaped interference fringe systems with contrary fringe spacing gradients. Via two Doppler frequency evaluations the non-incremental position (i.e. distance) and the tangential velocity of rotating bodies are determined simultaneously. The distance uncertainty is in contrast to e.g. triangulation in principle independent of the object velocity. This unique feature allows micrometer resolutions of fast moved rough surfaces. The novel sensor was applied at turbo machines in order to control the tip clearance. The measurements at a transonic centrifugal compressor were performed during operation at up to 50,000 rpm, i.e. 586 m/s velocity of the blade tips. Due to the operational conditions such as temperatures of up to 300 °C, a flexible and robust measurement system with a passive fiber-coupled sensor, using diffractive optics, has been realized. Since the tip clearance of individual blades could be temporally resolved an analysis of blade vibrations was possible. A Fourier transformation of the blade distances results in an average period of 3 revolutions corresponding to a frequency of 1/3 of the rotary frequency. Additionally, a laser Doppler distance sensor using two tilted fringe systems and phase evaluation will be presented. This phase sensor exhibits a minimum position resolution of ?z = 140 nm. It allows precise in-situ shape measurements at grinding and turning processes.

Czarske, J.; Pfister, T.; Günther, P.; Büttner, L.

2009-06-01

157

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.

158

Characterising neovascularisation in fracture healing with laser Doppler and micro-CT scanning.  

Science.gov (United States)

Vascularity of the soft tissues around a bone fracture is critical for successful healing, particularly when the vessels in the medullary canal are ruptured. The objective of this work was to use laser Doppler and micro-computer tomography (micro-CT) scanning to characterise neovascularisation of the soft tissues surrounding the fracture during healing. Thirty-two Sprague-Dawley rats underwent mid-shaft osteotomy of the left femur, stabilised with a custom-designed external fixator. Five animals were killed at each of 2, 4 days, 1, 2, 4 and 6 weeks post-operatively. Femoral blood perfusion in the fractured and intact contralateral limbs was measured using laser Doppler scanning pre- and post-operatively and throughout the healing period. At sacrifice, the common iliac artery was cannulated and infused with silicone contrast agent. Micro-CT scans of the femur and adjacent soft tissues revealed vessel characteristics and distribution in relation to the fracture zone. Blood perfusion dropped immediately after surgery and then recovered to greater than the pre-operative level by proliferation of small vessels around the fracture zone. Multi-modal imaging allowed both longitudinal functional and detailed structural analysis of the neovascularisation process. PMID:23881721

Macdonald, W; Shefelbine, S J

2013-10-01

159

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)

2013-03-01

160

Verbesserung der Systemeigenschaften Eines Gepulsten Laser-Doppler-Anemometers Unter Beruecksichtigung Eines Optischen Verstaerkers (Improvement of System Properties of a Pulsed Laser Doppler Anemometer with Respect to an Optical Amplifier).  

Science.gov (United States)

The use of an optical detector preamplifier in a pulsed laser Doppler system operating at the wavelength 10.6 micrometers is investigated. Especially the possibility of improvement of the SNR (Signal to Noise Ratio) from the whole lidar system was examine...

S. Rahm

1993-01-01

 
 
 
 
161

Multipoint laser Doppler vibrometry with single detector: principles, implementations, and signal analyses.  

Science.gov (United States)

A 20-point laser Doppler vibrometer with single photodetector is presented for noncontact dynamic measurement. A 5×4 beam array with various frequency shifts is generated by a 1.55 ?m distributed feedback laser and four acousto-optic devices, and illuminating different points on vibrating objects. The reflected beams are coupled into a single-mode fiber by a pigtailed collimator and interfere with a reference beam. The signal output from a high-speed photodetector is amplified and then digitized by a high-speed analog-to-digital converter with a sampling rate of 1 gigasample per second (1 GS/s). Several methods are introduced to avoid the cross talk among different frequencies and extract the vibration information of 20 points from a one-dimensional signal. Two signal processing algorithms based on Fourier transform and windowed Fourier transform are illustrated to extract the vibration signals at different points. The experimental results are compared with that from a commercial single-point laser vibrometer. The results show simultaneous vibration measurement can be realized on multiple points using a single laser source and a single photodetector. PMID:21460890

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

2011-04-01

162

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

163

Laser Doppler and transcutaneous oximetry: modern investigations to assess drug efficacy in chronic venous insufficiency.  

Science.gov (United States)

During chronic venous insufficiency (CVI), microcirculatory changes, e.g. a decrease in transcutaneous oxygen pressure (tcpO2) and an increase in transcutaneous carbon dioxide pressure (tcpCO2), are implicated in the pathophysiology of trophic disorders leading ultimately to venous ulcers. Daflon 500 mg1, a micronized purified flavonoid fraction, has been shown to improve venous tone, capillary permeability and resistance, and lymphagogue activity at a daily dose of 2 tablets. To assess the effects of Daflon 500 mg on microcirculatory parameters by means of laser Doppler fluxmetry and transcutaneous oxiketry, a 3-month, double-blind, randomized, parallel-group study was carried out in 104 patients divided into 3 groups according to the daily dose: 1 tablet (group 1, n = 34), 2 tablets (group 2, n = 33), on 4 tablets (group 3, n = 37). All patients (mean age 43.7 +/- 13.1 years; 100 females, 4 males) included in the study were affected by mild CVI. They were followed for 90 days with visits at 1 month (day 28) and 3 months (day 90). At inclusion, there were no significant differences between groups as regards biometric data, mean tcpO2 (group 1, 62.7 +/- 4.5 mm Hg; group 2, 64.0 +/- 3.3 mm Hg; group 3, 64.1 +/- 3.5 mm Hg), mean tcpCO2 (group 1, 40.7 +/- 2.5 mm Hg; group 2, 39.3 +/- 2.9 mm Hg; group 3, 40.0 +/- 2.5 mm Hg) and laser Doppler parameters. Fourteen patients withdrew from the study (group 1, n = 4; group 2, n = 3; group 3, n = 7): 9 for reasons not related to treatment, 3 for adverse events, 2 because they were lost to follow-up. From day 0 to day 90, mean tcpO2 significantly increased (p Daflon 500 mg improved oximetric measurements and did not alter laser Doppler parameters. These data suggest that Daflon 500 mg, at the early stages of CVI, acts favourably on the microcirculatory disturbances also involved in the pathophysiology of more severe stages of CVI. PMID:8748889

Belcaro, G; Cesarone, M R; de Sanctis, M T; Incandela, L; Laurora, G; Février, B; Wargon, C; De Gregoris, P

1995-01-01

164

Phase-resolved laser Raman scattering and laser Doppler velocimetry applied to periodic instabilities in a gas turbine model combustor  

Science.gov (United States)

The understanding of periodic flame instabilities belongs to the major challenges in modern combustion research and technology and is of special importance for lean premixed gas turbine combustion. This paper presents experimental investigations in a gas turbine model combustor using laser diagnostic techniques. A partially premixed CH4/air flame operated at a thermal power of 10 kW at atmospheric pressure and an overall equivalence ratio of 0.75, which exhibited thermoacoustic oscillations at a frequency of 290 Hz, was investigated. Phase-locked laser Raman scattering was applied in order to determine the major species concentrations, temperature, and mixture fraction. In addition, laser Doppler velocimetry (LDV) was used separately for the measurement of the axial and radial velocity components. The measurements revealed pronounced phase-dependent variations of the velocity and the temperature, species, and mixture fraction distributions. The combined Raman and LDV results also enabled the determination of molecular species fluxes which showed that the fuel and air supply rates both varied during an oscillation cycle by ±33% but with a phase shift of 80 between them. The correlations between temperature and mixture fraction revealed strong deviations from equilibrium composition and temperature, and their phase-dependent changes reflected the transport and mixing processes near the nozzle. The emphasis of the paper lies on the demonstration of the potential of phase-locked laser Raman scattering for the study of phenomena of periodic flame instabilities.

Duan, X. R.; Meier, W.; Weigand, P.; Lehmann, B.

2005-03-01

165

A solid state laser system for Doppler-free spectroscopy of muonium  

Energy Technology Data Exchange (ETDEWEB)

The thesis describes a new high precision measurement of the 1S-2S transition frequency in muonium, carried out at the ISIS facility at the Rutherford Appleton Laboratory, using a solid-state laser system. The focus of the thesis is mainly the work carried out on the pulsed part of the laser system. The transition frequency is measured by the Doppler-free spectroscopy. The two-photon 1S-2S transition is detected by observing the positive muon released after subsequent photo-ionisation from the 2S state by a third photon from the same laser field. An accurate frequency standard for the experiment was provided by a Doppler-free transition in molecular iodine. A cw Ti:sapphire laser operating around 732 nm locked to this reference transition provided a stable output for injection seeding the pulsed alexandrite laser. This has been optimised and modified to achieve a stable operation in a single transverse and longitudinal mode. There were stringent requirements on the laser pulse timing relative to an external trigger in order to synchronise the laser pulse with the muon pulse from the ISIS facility. A method of cavity length stabilisation, which reduced the jitter of the laser from approximately 20 {mu}s to 100ns and allowed us to trigger the laser externally, is described. This was performed in two stages using an intracavity, piezo-mounted, quartz plate and two fast, electro-optic modulators. The frequency chirp of the laser output, measured using a heterodyne technique 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. (author)

Bakule, P

1998-07-01

166

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

International Nuclear Information System (INIS)

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 Cramer 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

2008-07-20

167

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

1986-01-01

168

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

169

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

170

Effect of timolol on sub-foveal choroidal blood flow using laser Doppler flowmetry  

Science.gov (United States)

Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours. Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated eyes were observed.

Palanisamy, Nithiyanantham; Rovati, Luigi; Cellini, Mauro; Gizzi, Corrado; Strobbe, Ernesto; Campos, Emilio; Riva, Charles E.

2011-02-01

171

Measurement of fluid velocity development in laminar pipe flow using laser Doppler velocimetry  

International Nuclear Information System (INIS)

In this paper we present a non-intrusive experimental approach for obtaining velocity gradient profiles in a transparent smooth pipe under laminar flow conditions (Re = 925) using a laser Doppler velocimeter (LDV). Measurements were taken within the entrance region of the pipe at l = 300 mm and l = 600 mm from the pipe inlet, in addition to measurements of the fully developed flow at l = 1800 mm. The obtained results show how the velocity profile from upstream of the pipe develops into a classical laminar profile downstream, which matches the theoretical profile well. Additionally, a brief summary of historical information about the development of flow measurement techniques, in particular LDV, is provided. (paper)

2013-09-01

172

Flow characteristics in spacer grids measured by rod-embedded fiber laser doppler velocimetry  

International Nuclear Information System (INIS)

Precise measurement of velocity in fuel bundles is required to improve the thermal-hydraulic properties of Pressurized Water Reactor (PWR) spacer grids. To better understand the cross-flow characteristics in rod bundles for developing spacer grids, we used the rod-embedded fiber laser Doppler velocimetry (rod LDV) to measure the flow velocities inside the spacer grid flow channels. As the result of measurement, we found that the flow distribution inside the spacer grid depends on the local flow resistance of the grid straps and is clearly affected by the presence of a mixing vane. We also clarified the relationship between cross-flow velocity in the fuel bundle downstream of the spacer grid and the axial flow inside the spacer grid. (author)

2007-02-01

173

Simultaneous 3D Laser Doppler Velocimeter (LDV) measurements in the wake of bluff bodies  

Science.gov (United States)

Turbulence fluctuations were measured in the near and far wake of a nonaxisymmetric blunt afterbody by a 3D, 3 color laser Doppler velocimeter. Results show that this velocimeter is operational and capable of measuring small velocities compared to the freestream velocity. Data obtained behind an afterbody including a triangular base show that this system can provide information of flowfields of three-dimensional nature. However, since there is an increase in the amount of information in 3D flow, further data reduction and complementary analysis are needed to reconstruct the entire velocity field and to clarify the different accuracy of the velocity components, especially in order to explain the difference of turbulence level observed at the stations where z is different from zero.

Berner, C.

1986-07-01

174

Elasticity Evaluation of Regenerating Cartilage Sample Based on Laser Doppler Measurement of Ultrasonic Particle Velocity  

Science.gov (United States)

It is important for regenerative medicine to evaluate the maturity of regenerating tissue. In the maturity evaluation of regenerating cartilage, it is useful to measure the temporal change of elasticity because the maturity of regenerating tissue is closely related to its elasticity. In this study, an elasticity evaluation method for the extracted regenerating cartilage sample, which is based on the laser Doppler measurement of ultrasonic particle velocity, was experimentally investigated using agar-based phantoms with different elastic moduli and the regenerating cartilage samples extracted from beagles in animal experiments. In addition, the experimentally-obtained elasticity was compared with the result of a static compression test. These results verified the feasibility of the proposed method in the elasticity evaluation of regenerating cartilage samples.

Nitta, Naotaka; Misawa, Masaki; Homma, Kazuhiro; Shiina, Tsuyoshi

2012-07-01

175

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

176

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

2013-12-01

177

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

Energy Technology Data Exchange (ETDEWEB)

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.

Yang, C. [Temasek Laboratories and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China); Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621900 (China); Guo, M.; Liu, H.; Yan, K.; Xu, Y. J.; Fu, Y., E-mail: fuyuoptics@gmail.com [Temasek Laboratories and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); Miao, H. [Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China)

2013-12-15

178

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

179

Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation  

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 can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation.

Campo, Adriaan; Dirckx, Joris

2014-05-01

180

Efficient sub-Doppler transverse laser cooling of an indium atomic beam  

Energy Technology Data Exchange (ETDEWEB)

Laser cooled atomic gases and atomic beams are widely studied samples in experimental research in atomic and optical physics. For the application of ultra cold gases as model systems for e.g. quantum many particle systems, the atomic species is not very important. Thus this field is dominated by alkaline, earthalkaline elements which are easily accessible with conventional laser sources and have convenient closed cooling transition. On the other hand, laser cooled atoms may also be interesting for technological applications, for instance for the creation of novel materials by atomic nanofabrication (ANF). There it will be important to use technologically relevant materials. As an example, using group III atoms of the periodical table in ANF may open a route to generate fully 3D structured composite materials. The minimal requirement in such an ANF experiment is the collimation of an atomic beam which is accessible by one dimensional laser cooling. In this dissertation, I describe transverse laser cooling of an Indium atomic beam. For efficient laser cooling on a cycling transition, I have built a tunable, continuous-wave coherent ultraviolet source at 326 nm based on frequency tripling. For this purpose, two independent high power Yb-doped fiber amplifiers for the generation of the fundamental radiation at {lambda}{sub {omega}} = 977 nm have been constructed. I have observed sub-Doppler transverse laser cooling of an Indium atomic beam on a cycling transition of In by introducing a polarization gradient in the linear-perpendicular-linear configuration. The transverse velocity spread of a laser-cooled In atomic beam at full width at half maximum was achieved to be 13.5{+-}3.8 cm/s yielding a full divergence of only 0.48 {+-} 0.13 mrad. In addition, nonlinear spectroscopy of a 3-level, {lambda}-type level system driven by a pump and a probe beam has been investigated in order to understand the absorption line shapes used as a frequency reference in a previous two-color spectroscopy experiment. For the analysis of this atomic system, I have applied a density matrix theory providing an excellent basis for understanding the observed line shapes. (orig.)

Kim, Jae-Ihn

2009-07-23

 
 
 
 
181

Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp  

Science.gov (United States)

The paper investigates the use of optogalvanic (OG) measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser-induced fluorescence signals from an arcjet plume. It is shown that, even with non-Doppler-free OG detection, accuracy to better than 10 MHz is possible but that, depending on the experiment geometry, corrections of 10-35 MHz may be necessary to offset small axial drift velocities of neutral atoms in the hollow cathode lamp.

Ruyten, Wilhelmus M.; Keefer, Dennis

1992-01-01

182

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. The results of the laser anemometry are presented in the form of two-dimensional Mach number distributions. The good agreement with analogous results obtained by classical probe measurements and model calculations indicate that the laser anemometer can be successfully utilized for the quantitative analysis of shock-boundary layer interferences about transonic wing profiles.

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

1983-12-01

183

Field performance of an all-semiconductor laser coherent Doppler lidar  

DEFF Research Database (Denmark)

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.

Rodrigo, Peter John; Pedersen, Christian

2012-01-01

184

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

Energy Technology Data Exchange (ETDEWEB)

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.

Neufeld, G.R.; Galante, S.R.; Whang, J.M.; DeVries, D.; Baumgardner, J.E.; Graves, D.J.; Quinn, J.A.

1988-03-01

185

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

186

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

187

Use of Wigner-Ville transformations for fluid particles in laser Doppler flow accelerometry  

International Nuclear Information System (INIS)

Flow acceleration with Lagrangian description is crucial to understanding particle movements in turbulent jet flows or dissipation statistics in isotropic turbulence. Laser Doppler anemometry is regarded as a suitable experimental tool for measuring flow acceleration, because scattering particles generate trajectories in the measurement volume, which process gives rise to flow acceleration at a fixed measuring point with the Lagrangian description. The most useful algorithm for processing Doppler signals is either the quadrature demodulation technique (QDT) or the iterative parametric method (alternatively, the minimization of least squares, LSM) as in the literature. In the present study, another algorithm using the Wigner-Ville transform (W-V) is introduced to give more accurate estimation of flow acceleration than the QDT or the LSM. Five signal-processing algorithms, including the QDT, the LSM, the MC (maximization of correlation), and the W-V, were compared with each other in experiments with an impinging air jet flow with a cylindrical rod and a round free-air jet flow. Mean flow acceleration distribution in the stream wise direction was mainly investigated. Processing speeds for the above-mentioned signal-processing algorithms were checked to find the best algorithm, which has best performance with short processing time. Although QDT was found to be an accurate algorithm with short processing time, it has limited applications to flows with large acceleration and high SNR. The MC was also found to be a good algorithm with moderate processing speed, which can be useful in flows with low SNR because the MC is an iterative parametric method. The W-V gave the most accurate values for flow acceleration; however, the processing time for this method was the slowest among the signal-processing algorithms

2012-03-01

188

Evaluation of algorithms for microperfusion assessment by fast simulations of laser Doppler power spectral density  

Science.gov (United States)

In classical laser Doppler (LD) perfusion measurements, zeroth- and first-order moments of the power spectral density of the LD signal are utilized for the calculation of a signal corresponding to the concentration, speed and flow of red blood cells (RBCs). We have analysed the nonlinearities of the moments in relation to RBC speed distributions, parameters of filters utilized in LD instruments and the signal-to-noise ratio. We have developed a new method for fast simulation of the spectrum of the LD signal. The method is based on a superposition of analytically calculated Doppler shift probability distributions derived for the assumed light scattering phase function. We have validated the method by a comparison of the analytically calculated spectra with results of Monte Carlo (MC) simulations. For the semi-infinite, homogeneous medium and the single Doppler scattering regime, the analytical calculation describes LD spectra with the same accuracy as the MC simulation. The method allows for simulating the LD signal in time domain and furthermore analysing the index of perfusion for the assumed wavelength of the light, optical properties of the tissue and concentration of RBCs. Fast simulations of the LD signal in time domain and its frequency spectrum can be utilized in applications where knowledge of the LD photocurrent is required, e.g. in the development of detectors for tissue microperfusion monitoring or in measurements of the LD autocorrelation function for perfusion measurements. The presented fast method for LD spectra calculation can be used as a tool for evaluation of signal processing algorithms used in the LD method and/or for the development of new algorithms of the LD flowmetry and imaging. We analysed LD spectra obtained by analytical calculations using a classical algorithm applied in classical LD perfusion measurements. We observed nonlinearity of the first moment M1 for low and high speeds of particles (v 10 mm s-1). It was also noted that the first moment M1 is less sensitive to the change of the mean RBC speed for flat speed distributions. The low-pass filter frequency f2 implemented in the LD instrument has a significant influence on the first moment of the spectrum. In particular, for a cut-off frequency lower than 10 kHz the M1 value is strongly underestimated.

Wojtkiewicz, S.; Liebert, A.; Rix, H.; Maniewski, R.

2011-12-01

189

Laser-Doppler spectrum decomposition applied for the estimation of speed distribution of particles moving in a multiple scattering medium  

Science.gov (United States)

Recently, a method for the estimation of speed distribution of particles moving in an optically turbid medium has been proposed. The method allows potentially absolute measurement of speed of the particles and can be applied in laser-Doppler perfusion measurements. However, the decomposition technique was limited to short source-detector separations for which the assumption that one photon is Doppler scattered not more than once is fulfilled. In the present paper we show a generalized decomposition technique in which photons can be scattered more than once. We show the theoretical background for decomposition in such a case. We apply a decomposition method for the analysis of laser-Doppler spectra obtained by Monte Carlo simulations. This analysis allows showing noise limits in which the technique can be effectively applied in analysis of measured spectra. We propose an approximated scattering model based on the assumption that for one photon consecutive Doppler scattering events occur on particles moving with the same speed, and we show that this approximation does not influence significantly the uncertainty of the resulting speed distribution. The proposed decomposition procedure is validated in measurements on a physical flow model. The decomposition procedure is also validated by analysis of spectra measured on a physical phantom using laser-Doppler flow meter (Oxford Optronix, UK). A diluted solution of milk was pumped through a tube fixed in an optically turbid material with speed varying from 0 mm s-1 to 4 mm s-1. We observed a linear relation between actual speed of milk solution and speed estimated from results of spectra decomposition.

Wojtkiewicz, S.; Liebert, A.; Rix, H.; ?o?ek, N.; Maniewski, R.

2009-02-01

190

Coriolis-type mass flowmeter  

International Nuclear Information System (INIS)

A mass flowmeter of the Coriolis type is described comprising: A. a single turn flow loop formed by a pipe having a pair of arcuate legs the loop is supported on a frame whereby the loop is free to vibrate at its natural resonance frequency; B. a self-sufficient electromagnetic ballistic vibrator mounted on the loop at the vertex. The vibrator has a mass that oscillates to cause the loop to vibrate at its resonance frequency; C. means to feed a fluid to be metered through the vibrating loop to cause the loop to undergo tortional oscillation as a function of mass flow: D. a pair of strain gauges mounted on the respective legs of the loop whereby in the absence of flow, the gauges yield equal signals and during flow they yield signals of different magnitude as a function of mass flow; E. means to apply the signals from the gauges to a differential amplifier whose output is substantially proportional to the mass flow rate; and F. means responsive to the differential amplifier output to provide a mass flow rate reading

1987-01-01

191

Sub-Doppler diode laser saturated absorption spectroscopy of barium in a low-pressure graphite furnace  

International Nuclear Information System (INIS)

As a first step toward developing an optical isotope abundance measurement technique, sub-Doppler saturated absorption spectroscopy has been demonstrated by using a scanning diode laser as a tunable light source and a low-pressure graphite furnace for sample atomization. Spectral linewidths were reduced by a factor of 49 from the pressure-broadened, Doppler-limited value of 2.8 GHz to 57 MHz. This reduction in linewidths was accompanied by a 60-fold increase in detection limits, mainly due to increased loss of analyte through rapid diffusion at the low pressure used to minimize collisional broadening. Some residual homogeneous broadening was observed, which is primarily attributed to laser power broadening. copyright 1998 Society for Applied Spectroscopy

1998-09-01

192

Kombineret laser Doppler flowmetri og spectrophotometri som metode til vurdering af mikrocirculation.  

DEFF Research Database (Denmark)

Kombineret laser Doppler flowmetri og spectrophotometri som metode til vurdering af mikrocirculation Berggren, MB, reservelæge, Karkirurgisk Afdeling, Kolding, mette.marie.berggren.olsen@slb.regionsyddanmark.dk; Houlind, K, lektor, afdelingslæge, Ph.d., Karkirurgisk afdeling, Kolding, kim.christian.houlind@slb.regionsyddanmark.dk; Sørensen, HB, lektor, speciallæge, Ph.d., Klinisk Institut, �rhus Universitetshospital, hanne.Birke@ki.au.dk Foredragsholder: Berggren, MB, reservelæge, Karkirurgisk Afdeling, Kolding. Formål og baggrund: Postoperativ iskæmi er den største trussel mod autologe, mikrovaskulære transplantater. Da venøs occlusion er mere skadelig end arteriel, er det ønskeligt med en metode, som hurtigt og sikkert kan både afsløre og skelne mellem venøs og arteriel thrombose. O2C er en non-invasiv metode, som ved laser Doppler flowmetri og photospectroscopi måler flow, saturation, relativ hæmoglobin og flowhastighed i 2 og 8mm dybde. Tidligere in-vitro studier , indikerer, at metoden kan være et værdifuldt værktøj til monitorering af vævstransplantater, som giver mulighed for hurtigt at detektere vaskulære problemer, samt at skelne mellem venøs og arterielaflukning. Design: Deskriptivt, dyreeksperimentelt studie. Metoder: På 8 grise løftes højre og venstre rectusmuskel som fri lap og randomiseres til venøs eller arteriel okklusion. Der påsættes tang og på det relevante kar, og foretages O2C målinger hvert 5. min de første 30 min. og herefter hvert 15. min. Efter 3 timer fjernes tangen og der måles igen hvert 5. min. i 30 min. Data analyseres efterfølgende Vigtigste Variable: �ndringer i flow, hæmoglobin og saturation ved venøs og arteriel aflukning og reperfusion. Forventede resultater: Vi forventer at se, at en stigning i rHgb, samt et fald i flow og saturation i både 2 og 8mm dybde på lapperne med venøs obstruktion. På lapper med arteriel occlusion forventes et abrupt fald i flow og saturation. Såfremt ændringerne findes signifikante udregnes grænseværdier og SD.

Olsen, Mette Marie Berggreen; Sørensen, Hanne Birke

193

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

194

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

195

Microvascular involvement in systemic sclerosis: laser Doppler evaluation of reactivity to acetylcholine and sodium nitroprusside by iontophoresis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVES—To investigate the skin vasodilatory response to iontophoretically applied acetylcholine (Ach), an endothelium dependent vasodilator, and to sodium nitroprusside (SNP), an endothelium independent vasodilator, in patients with systemic sclerosis (SSc).?METHODS—Eleven SSc patients were preliminarily studied (10 females, mean age 40.5; mean disease duration 6.5 years), and 16 age and sex matched control subjects. By means of laser Doppler flowmetry skin blood flow was eva...

Civita, L.; Rossi, M.; Vagheggini, G.; Storino, F.; Credidio, L.; Pasero, G.; Giusti, C.; Ferri, C.

1998-01-01

196

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

197

Investigation of Contact Acoustic Nonlinearity in Delaminations by Shearographic Imaging, Laser Doppler Vibrometric Scanning and Finite Difference Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Full-field dynamic shearography and laser Doppler vibrometric scanning are used to investigate the local contact acoustic nonlinear generation of delamination-induced effects on the vibration of a harmonically excited composite plate containing an artificial defect. Nonlinear elastic behavior caused by the stress-dependent boundary conditions at the delamination interfaces of a circular defect is also simulated by a 3-D second-order, finite-difference, staggered-grid model (displacement-stres...

Sarens, Bart; Verstraeten, Bert; Glorieux, Christ; Kalogiannakis, Georgios; Hemelrijck, Danny

2010-01-01

198

Blood perfusion studies on basal cell carcinomas in conjunction with photodynamic therapy and cryotherapy employing laser-Doppler perfusion imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Superficial blood perfusion mas monitored using laser-Doppler perfusion imaging in connection with a phase LII clinical trial comparing photodynamic therapy, utilizing topically applied aminoleuvlinic acid, with cryotherapy of basal cell, carcinomas. A total of 526 images mere recorded before and immediately after the treatment and during the follow-up period. Before treatment, the lesions exhibited a blood perfusion 3+/-2 times that in normal tissue. Both treatment modalities induced an incr...

Enejder, A. M. K.; Af Klinteberg, C.; Wang, I.; Andersson-engels, Stefan; Bendsoe, N.; Svanberg, Sune; Svanberg, Katarina

2000-01-01

199

Measurement of flow velocities in a model of blood vessel by laser doppler anemometer (1D LDA)  

International Nuclear Information System (INIS)

In this paper results of measuring velocities in a simple profile by laser doppler anemometer (1D LDA) are presented. Further work on the project will include research in models of normal and changed configurations related to human pathology. The profile of flow velocities and level of turbulence are determined for a cylindrical tube with 18 mm diameter, which approximately presents an usual radius of aorta. (author)

1995-06-06

200

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

 
 
 
 
201

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

202

Evaluation of a dual beam laser Doppler displacement meter retrofitted to a coordinate measuring machine. Final report  

Energy Technology Data Exchange (ETDEWEB)

A dual beam laser Doppler displacement measuring system was mounted to a fixed-table, cantilever-type coordinate measuring machine (CMM) to establish the feasibility of real time angular error correction for each CMM axis. The performance improvement was evaluated relative to the CMM`s standard scales. The dual beam system proved to have no advantage over a single beam laser due to an inability to measure the actual angular errors at the probe location, but showed potential for substantial accuracy improvement over the standard CMM scales when geometry errors were software corrected.

Ramsdale, S.J.; Hanshaw, R.A.

1997-05-01

203

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

2002-06-01

204

Laser Doppler vibrometry measures of physiological function: evaluation of biometric capabilities  

Science.gov (United States)

A novel approach using mechanical physiological activity as a biometric marker is described. Laser Doppler Vibrometry is used to sense activity in the region of the carotid artery, related to arterial wall movements associated with the central blood pressure pulse. The non-contact basis of the LDV method has several potential benefits in terms of the associated non-intrusiveness. Several methods are proposed that use the temporal and/or spectral information in the signal to assess biometric performance both on an intra-session basis, and on an intersession basis involving testing repeated after delays of 1 week to 6 months. A waveform decomposition method that utilizes principal component analysis is used to model the signal in the time domain. Authentication testing for this approach produces an equal-error rate of 0.5% for intra-session testing. However, performance degrades substantially for inter-session testing, requiring a more robust approach to modeling. Improved performance is obtained using techniques based on time-frequency decomposition, incorporating a method for extracting informative components. Biometric fusion methods including data fusion and information fusion are applied in multi-session data training model. As currently implemented, this approach yields an inter-session equal-error rate of 9%.

Chen, Mei; O'Sullivan, Joseph A.; Singla, Naveen; Sirevaag, Erik J.; Rohrbaugh, John W.

2009-05-01

205

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.

2010-05-28

206

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

2005-05-07

207

Drug-induced zeta potential changes in liposomes studied by laser Doppler spectroscopy.  

Science.gov (United States)

The technique of laser Doppler spectroscopy is used to measure the electrophoretic mobility of liposomes under the influence of one beta-blocking agent and three local anesthetics. All four drugs decrease the mobility (i.e., the zeta potential) of negatively charged phospholipids (soybean lipids, phosphatidylserine and cardiolipin). The mobility of electrostatically neutral pure phosphatidylcholine (zero mobility under control conditions at pH 7 and 4) is increased linearly with the logarithm of drug concentration, indicating binding and incorporation of positively charged drug molecules. The sequence of strength of activity, measured by zeta-potential changes, corresponds to that found in biological tissues: propranolol greater than tetracaine greater than lidocaine greater than procaine. For purely negatively charged lipids (phosphatidylserine, cardiolipin) the activity of the drug is higher at acidic pH, (pH 4), while for electrostatically neutral (phosphatidylcholine) or partly neutral (soybean) lipid liposomes drug activity is about the same at pH 9, 7 and 4. A Hill plot of the data reveals noncooperative drug binding. From the line width of the scattering power spectrum the mean particle radius and the average interparticle distance in the samples are determined. PMID:6114748

Schlieper, P; Medda, P K; Kaufmann, R

1981-06-22

208

A rotating laser-Doppler anemometry system for unsteady relative flow measurements in model centrifugal impellers  

Energy Technology Data Exchange (ETDEWEB)

The behavior of the relative flow in centrifugal turbomachines is extremely complex due to the existence of various fluid dynamic phenomena and their interaction. At design and off-design operating conditions, the relative flow is subject to stationary unsteadiness, which includes the flow separation and wakes associated with passage pressure gradients, secondary flows, and boundary layer stability. It is also subject to periodic unsteadiness from the rotating stall and the cyclic flow phenomena induced by the casing. This paper describes the mechanical and optical design of a rotating laser-Doppler anemometry system, which allows direct measurement of the relative flow by means of an optical derotator. By isolating the impeller rotational frequency form the sampling frequency, it allows direct time-average measurements of the stationary behavior of the relative flow along with the ensemble (phase)-averaged measurements of its periodic behavior. Its success is demonstrated with measurements conducted in a low specific speed centrifugal impeller fitted with a single volute. Sample results of the time-averaged blade-to-blade variation of total relative velocities along with their associated turbulence intensities are reported. The (periodic) cyclic variations of the impeller exit flow, induced by the volute at low flow rates, are also presented for the suction and pressure sides.

Abramian, M. (Pratt Whitney Canada, Mississauga, Ontario (Canada)); Howard, J.H.G. (Univ. of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering)

1994-04-01

209

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

210

A preliminary report on the use of laser-Doppler flowmetry during tethered spinal cord release.  

Science.gov (United States)

Neurological deterioration in the tethered cord syndrome has been postulated to result from a compromise of blood flow in the distal spinal cord. In order to evaluate vascular perfusion in human subjects, a new technique of laser-Doppler flowmetry was used to monitor continuously the microcirculation of the distal spinal cord during surgery for tethered cord release in 10 children. For further comparison, five children undergoing selective dorsal rhizotomy were also monitored. In the tethered cord syndrome group, spinal cord blood flow before untethering was a mean of 12.6 ml/min per 100 g of tissue and increased in all cases after release to a mean of 29.4 ml/min per 100 g of tissue. All patients improved neurologically. The selective dorsal rhizotomy group had a preoperative mean spinal cord blood flow of 30.8 ml/min per 100 g of tissue, which was not altered by the operative procedure. Significant improvement occurs in distal spinal cord blood flow after tethered cord release, which may be representative of an important mechanism in the pathophysiology of the tethered cord syndrome. PMID:8437659

Schneider, S J; Rosenthal, A D; Greenberg, B M; Danto, J

1993-02-01

211

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

212

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.

Pinotti, Marcos; Faria, Edna M. de.

213

Sample entropy of laser Doppler flowmetry signals increases in patients with systemic sclerosis.  

Science.gov (United States)

Associated to reactivity tests, laser Doppler flowmetry (LDF) emphasizes abnormal skin microvascular function in diseases affecting digits, such as Raynaud's phenomenon (RP) and systemic sclerosis (SSc). However, baseline perfusion value does not discriminate between disease states. We study if LDF sample entropy (SampEn) allows distinguishing healthy subjects, RP and SSc patients. LDF measurements were performed on finger pad and forearm of 108 subjects (27 controls, 28 RP patients, 53 SSc patients), before and after local thermal hyperemia. We also assessed the reproducibility of SampEn [expressed as within-subject coefficients of variation (CV) and intra-class correlation coefficients (ICC)]. Baseline SampEn is significantly increased in patients with SSc compared to RP and controls on finger pad [0.49 (0.19), 0.38 (0.14) and 0.36 (0.15), respectively; P<0.002], but not on forearm. However, local thermal hyperemia increased SampEn at all sites and for all groups. Finally, reproducibility of SampEn computed on two baseline segments was acceptable (CV=26%, ICC=0.63). SampEn of skin blood flow at rest is increased on finger pad of patients with SSc but not on forearm. This is consistent with the pathophysiology of the disease, which predominantly affects digital microcirculation in most patients. SampEn of LDF signal could be a reproducible tool to predict digital microvascular impairment. PMID:21664914

Figueiras, E; Roustit, M; Semedo, S; Ferreira, L F Requicha; Crascowski, J L; Humeau, A

2011-09-01

214

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

215

Assessment of skin microcirculation by laser Doppler flowmetry in systemic sclerosis patients  

Science.gov (United States)

Introduction First lesions to occur in the course of systemic sclerosis (SSc) involve microcirculation. Aim The study involved assessment of the suitability of laser Doppler flowmetry (LDF) in examination of the performance of skin microcirculation in the distal portion of the upper extremity in SSc patients. Material and methods Overall the study involved 27 patients with systemic sclerosis. The control group comprised age – and gender-matched 27 healthy individuals. All the study subjects underwent microcirculation perfusion measurement at rest (rest flow – RF) as well as microcirculatory flow challenge tests – reactive hyperaemia test (RHT) and thermal stimulation test (TST). Results The study did not show any differences in the skin microcirculation perfusion at rest between the test group and the control, while reactive hyperaemia test results revealed significantly lower skin microcirculation perfusion values during the cuff inflation in SSc patients, as compared to the controls. In the test group, a lower perfusion value was observed during secondary hyperaemia following cuff release. Comparative analysis of skin microcirculation perfusion changes during the thermal stimulation test revealed a significantly lower change of the perfusion value and longer time of return to the baseline in the test group as compared to the control group. Conclusions The study performed has shown the suitability of LDF in the assessment of the microangiopathy degree in systemic sclerosis patients. The skin perfusion value in SSc patients should be assessed on the basis of parameters obtained in microcirculation challenge tests.

Gos, Roman; Waszczykowska, Elzbieta; Dziankowska-Bartkowiak, Bozena; Jurowski, Piotr

2014-01-01

216

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 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

217

Turbo machine tip clearance and vibration measurements using a fibre optic laser Doppler position sensor  

Science.gov (United States)

This paper presents a novel fibre optic laser Doppler position sensor for single blade tip clearance and vibration measurements at turbo machines, which offers high temporal resolution and high position resolution simultaneously. The sensor principle is based on the generation of a measurement volume consisting of two superposed fan-like interference fringe systems with contrary fringe spacing gradients using wavelength division multiplexing. A flexible and robust measurement system with an all-passive fibre coupled measurement head has been realized employing diffractive and refractive optics. Measurements of tip clearance and rotor vibrations at a transonic centrifugal compressor performed during operation at up to 50 000 rpm (833 Hz) corresponding to 21.7 kHz blade frequency and 586 m s-1 blade tip velocity are presented. The results are in excellent agreement with those of capacitive probes. The mean uncertainty of the position measurement was around 20 µm and, thus, considerably better than for conventional tip clearance probes. Consequently, this sensor is capable of fulfilling the requirements for future active clearance control systems and has great potential for in situ and online tip clearance and vibration measurements at metallic and non-metallic turbine blades with high precision.

Pfister, T.; Büttner, L.; Czarske, J.; Krain, H.; Schodl, R.

2006-07-01

218

Application of a new laser Doppler imaging system in planning and monitoring of surgical flaps  

Science.gov (United States)

There is a demand for technologies able to assess the perfusion of surgical flaps quantitatively and reliably to avoid ischemic complications. The aim of this study is to test a new high-speed high-definition laser Doppler imaging (LDI) system (FluxEXPLORER, Microvascular Imaging, Lausanne, Switzerland) in terms of preoperative mapping of the vascular supply (perforator vessels) and postoperative flow monitoring. The FluxEXPLORER performs perfusion mapping of an area 9×9 cm with a resolution of 256×256 pixels within 6 s in high-definition imaging mode. The sensitivity and predictability to localize perforators is expressed by the coincidence of preoperatively assessed LDI high flow spots with intraoperatively verified perforators in nine patients. 18 free flaps are monitored before, during, and after total ischemia. 63% of all verified perforators correspond to a high flow spot, and 38% of all high flow spots correspond to a verified perforator (positive predictive value). All perfused flaps reveal a value of above 221 perfusion units (PUs), and all values obtained in the ischemic flaps are beneath 187 PU. In summary, we conclude that the present LDI system can serve as a reliable, fast, and easy-to-handle tool to detect ischemia in free flaps, whereas perforator vessels cannot be detected appropriately.

Schlosser, Stefan; Wirth, Raphael; Plock, Jan A.; Serov, Alexandre; Banic, Andrej; Erni, Dominique

2010-05-01

219

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 change between placebo (32.1 ± 2.7 BPU and capsaicin (115.7 ± 24.6 BPU applica- tion. Capsaicin application produced significant percentage change in dermal blood flow by 291.0 ± 85.3% from baseline, while the change was insignificant with placebo (13.2 ± 7.4%. Therefore, it is suggested that this technique which is technically sound, non-invasive and inexpensive can be adopted in various fields of research to determine blood flow changes and this technique can also be utilized to determine the antagonists of the mediators involved in capsaicin induced vasodilatation.

Sunil Kumar Reddy Khambam

2011-07-01

220

Doppler shift laser fluorescence spectroscopy of sputtered and evaporated atoms under Ar+ bombardment  

International Nuclear Information System (INIS)

The temperature dependence of the sputtering yield and velocity distribution of sputtered neutral Ca and Cr atoms has been studied by Doppler shift laser fluorescence spectroscopy (DSLFS) for 15-keV-Ar+ ion bombardment.These investigations have been performed in the search for thermal spike effects and radiation-enhanced sublimation in sputtering at elevated temperatures. Ca targets have been studied up to about 270 0C and Cr targets up to 750 0C. The shapes of the velocity distributions do not change in the respective temperature ranges for both target materials. Furthermore, the absolute yield of sputtered neutral ground state atoms does not increase with temperature.This indicates that no radiation-enhanced thermal contribution is of relevant importance. Moreover, we can explain the velocity distributions in both cases by the linear cascade theory of sputtering. The thermal contribution due to thermal evaporation increases drastically above 230 0C for Ca and 550 0C for Cr. In both cases the corresponding velocity distribution can be fitted by a Boltzmann distribution

1985-01-01

 
 
 
 
221

Flow rate measurement of buoyancy-driven exchange flow by laser Doppler velocimeter  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation was carried out for the buoyancy-driven exchange flow in a narrow vented cylinder concerning the air ingress process during a standing pipe rupture in a high-temperature gas-cooled reactor. In the present study, the evaluation method of exchange flow was developed by measuring the velocity distribution in the cylinder using a laser Doppler velocimeter. The experiments were performed under atmospheric pressure with nitrogen as a working fluid. Rayleigh numbers ranged from 2.0x10[sup 4] to 2.1x10[sup 5]. The exchange flow fluctuated irregularly with time and space in the cylinder. It was found that the exchange velocity distribution along the horizontal axis changed from one-hump to two-hump distribution with increasing Rayleigh number. In the case that the hemisphere wall was cooler than the heated disk, the volumetric exchange flow rate was smaller than that in the case where the hemisphere wall and the heated disk were at the same temperature. (author).

Fumizawa, Motoo (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment)

1993-11-01

222

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

223

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

224

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

225

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.)

1977-01-01

226

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

227

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)

1999-06-01

228

Evaluation of two sympathetic cutaneous vasomotor reflexes using laser Doppler fluxmetry.  

Science.gov (United States)

Disturbances in sympathetic cutaneous vasomotor reflexes may be of pathogenetic importance in several microvascular problems. Laser Doppler fluxmetry (LDF) enables one to study the influence of sympathetic reflexes on skin blood flow. A matter of concern is the high variability of skin blood flow and its reactivity to sympathetic reflex test resulting in a poor reproducibility. In this study we evaluated two sympathetic stimulation tests, distant cooling and inspiratory gasp, and their influence on LDF-measured skin blood flow of the pulp of the big toe in 63 healthy volunteers. No age or sex dependency of the LDF test results was found. Absolute and relative LDF decrease during distant cooling was highly variable between the subjects (LDF decrease, mean +/-SD: 0.7 +/- 5.3%) compared to an LDF decrease of 46.5 +/- 3.1% during an inspiratory gasp test. The reproducibility, however, was better for the distant cooling test [coefficient of variation (CV): distant cooling: 5.8%, inspiratory gasp test: 35.4%]. With the use of a thermostatically controlled LDF probe holder fixed at a temperature of 36 degrees C, the short-term reproducibility of the two sympathetic vasomotor tests did not improve, probably because of a steady increase in baseline skin blood flow during the test. Surprisingly long-term variability of the percentage LDF decrease during the inspiratory gasp test, performed with the heated LDF probe, was lower compared to the short-term variability (CV 19.2 vs. 39.0%, p reactivity with a heated LDF probe (36 degrees C) did not improve reproducibility. PMID:8856385

Netten, P M; Wollersheim, H; van den Broek, P; van der Heijden, H F; Thien, T

1996-01-01

229

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

230

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

231

Linking water surface roughness to velocity patterns using terrestrial laser scanning and acoustic doppler velocimetry  

Science.gov (United States)

There are well established links between water surface characteristics and hydraulics. Biotope identification is currently an important part of the River Habitat Survey in England and Wales. Their differentiation is based upon recognition of a family of flow features exhibited on the water surface. Variability in this water surface ‘roughness' is dependent upon the interaction of flow with boundary roughness and flow depth. Past research that has attempted to differentiate biotopes based upon differences in Froude number (Fr) and Reynolds number (Re), however this linkage has only been limited to local analysis between flow velocity, depth and roughness. Milan et al. (2010) have recently demonstrated that terrestrial laser scanning (TLS) can be applied to produce fully quantitative maps of hydraulic habitat, based upon defined water surface roughness delimeters. However the nature of the linkages between water surface roughness, flow velocity and depth are still poorly understood, particularly at the reach-scale. This study attempts to provide a full spatial picture of the links between water surface roughness, flow depth and velocity. A Sontek Acoustic Doppler Velocity Profiler (ADVP) was used to provide detailed information on vertical velocity and water depth for a 300 m reach of the gravel-bed River Wharfe, Yorkshire, UK. Simultaneous to the ADVP measurements, a Riegl LMS-Z210 TLS was used to take a series of first return scans of the water surface. Categorisation of the point cloud elevation data for the water surface was achieved through the allocation of moving window standard deviation values to a regular grid, thus defining water surface roughness. The ADVP data demonstrate gross reach-scale variation in velocity and depth linked to bedforms, and more localised spatial and temporal variation within biotope units. The ADVP data was used to produce reach-scale maps of Fr and Re. The extent to which water surface roughness defined biotopes mapped onto these Fr and Re maps was then explored. The maps produced demonstrate a hydraulic picture that is far more complex than previously reported. It is concluded that a re-evaluation of the definition and use of biotopes to map instream river habitat is required. Reference Milan, D.J., Heritage, G.L., Large, A.R.G., Entwistle, N. 2010. Identification of hydraulic biotopes using terrestrial laser scan data of water surface properties. Earth Surface Processes & Landforms, 35, in press.

Heritage, George; Milan, David; Entwistle, Neil

2010-05-01

232

A new optical system for three-dimensional laser-Doppler-anemometry using an Argon-Ion and a dye laser  

Science.gov (United States)

A new optical system is described which allows three components of a fluid flow velocity vector to be measured simultaneously by means of laser Doppler anemometry. It is based on the use of an Argon-Ion laser which serves at the same time as the light source in a conventional two-component, two-color arrangement and as the pump source for a dye laser. With the dye laser a third interference fringe pattern is produced at an angle of 90 degrees with respect to the other two ones. The most important advantage as compared with competitive optics are the wide color separation and the nearly identical high power in all three fringe systems.

Pfeifer, H. J.

233

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

International Nuclear Information System (INIS)

Changes in skin blood flow measured by Laser Doppler flowmetry and changes in subcutaneous blood flow measured by 133Xenon 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 133Xenon 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 133Xenon 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 133Xenon method are not comparable, and that the Laser Doppler method is not useful in measuring local sympathetic mediated blood flow changes. (author)

1987-01-01

234

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

235

Tunable-Laser Derivative Spectroscopy on Spectral Lines with Combined Doppler and Collision Broadening.  

Science.gov (United States)

In derivative spectroscopy, the authors optimize the measurement sensitivity by using the maximum excursion of the derivative of the spectral absorption coefficient as a single spectral line is scanned. Results for lines with pure Doppler or Lorentz conto...

H. K. Chen K. G. P. Sulzmann S. S. Penner

1973-01-01

236

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

237

Monostatic coaxial 1.5 μm laser Doppler velocimeter using a scanning Fabry-Perot interferometer  

DEFF Research Database (Denmark)

We present a laser Doppler velocimeter (LDV) in monostatic coaxial arrangement consisting of off-the-shelf telecom-grade components: a single frequency laser (wavelength λ = 1.5 μm) and a high-finesse scanning Fabry-Perot interferometer (sFPI). In contrast to previous 1.5 μm LDV systems based on heterodyne detection, our sFPI-LDV has the advantages of having large remote sensing range not limited by laser coherence, high velocity dynamic range not limited by detector bandwidth and inherent sign discrimination of Doppler shift. The more optically efficient coaxial arrangement where transmitter and receiver optics share a common axis reduces the number of components and greatly simplifies the optical alignment. However, the sensitivity to unwanted backreflections is increased. To circumvent this problem, we employ a custom optical circulator design which compared to commercial fiber-optic circulator achieves ~40 dB reduction in strength of unwanted reflections (i.e. leakage) while maintaining high optical efficiency. Experiments with a solid target demonstrate the performance of the sFPI-LDV system with high sensitivity down to pW level at present update rates up to 10 Hz.

Rodrigo, Peter John; Pedersen, Christian

2013-01-01

238

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 monitoring. 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

2011-01-01

239

Time of correlation of low-frequency fluctuations in the regional laser Doppler flow signal from human skin  

Science.gov (United States)

The laser Doppler flowmetry allows the non-invasive assessment of the skin perfusion in real-time, being an attractive technique to study the human microcirculation in clinical settings. Low-frequency oscillations in the laser Doppler blood flow signal from the skin have been related to the endothelial, endothelial-metabolic, neurogenic and myogenic mechanisms of microvascular flow control, in the range 0.005-0.0095 Hz, 0.0095-0.021 Hz, 0.021-0.052 Hz and 0.052- 0.145 Hz respectively. The mean Amplitude (A) of the periodic fluctuations in the laser Doppler blood flow signal, in each frequency range, derived from the respective wavelet-transformed coefficients, has been used to assess the function and dysfunctions of each mechanism of flow control. Known sources of flow signal variances include spatial and temporal variability, diminishing the discriminatory capability of the technique. Here a new time domain method of analysis is proposed, based on the Time of Correlation (TC) of flow fluctuations between two adjacent sites. Registers of blood flow from two adjacent regions, for skin temperature at 32 0C (basal) and thermally stimulated (42 0C) of volar forearms from 20 healthy volunteers were collected and analyzed. The results obtained revealed high time of correlation between two adjacent regions when thermally stimulated, for signals in the endothelial, endothelial-metabolic, neurogenic and myogenic frequency ranges. Experimental data also indicate lower variability for TC when compared to A, when thermally stimulated, suggesting a new promising parameter for assessment of the microvascular flow control.

Folgosi-Correa, M. S.; Nogueira, G. E. C.

2012-05-01

240

Flow investigation by laser-Doppler velocimeter applied to vertical 180-degree bend of rectangular pipes, (1)  

International Nuclear Information System (INIS)

When water flows around 180"0-bend, centrifugal force acts on the flow resulting in secondary currents within the bend. This paper describes the results of an investigation of the spiral motion around the bend using a laser-Doppler velocimeter. Flow measurement in presence of swirl and manifestation of its velocity-vectors are difficult. This difficulty was solved by using a process such alike tomography and velocity-vactors could be represented stereo-graphically. Furthermore, an investigation was made of the occurrence of Dean's instability by measuring pressure distribution in the channel. This may be found to appear at lower Dean number in vertical channel than horizontal. (author)

1980-01-01

 
 
 
 
241

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

Science.gov (United States)

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.

Nouri, Joseph A.

242

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

1988-12-05

243

Air-coupled ultrasonic sensing of grass-covered vibrating surfaces; qualitative comparisons with laser Doppler vibrometry  

Science.gov (United States)

The paper addresses several sensitive issues concerning the use of air-coupled ultrasound to probe small vibrations of surfaces covered with low-lying vegetation such as grass. The operation of the ultrasonic sensor is compared to that of a laser Doppler vibrometer, in various contexts. It is shown that ambient air motion affects either system, albeit differently. As air speed increases, the acoustic sensor detects a progressively richer turbulent spectrum, which reduces its sensitivity. In turn, optical sensors are prone to tremendous signal losses when probing moving vegetation, due to randomly varying speckle patterns. The work was supported by the Office of Naval Research.

Petculescu, Andi G.; Sabatier, James M.

2004-04-01

244

Cross-sectional laser Doppler velocimetry with nonmechanical scanning of points spatially encoded by multichannel serrodyne frequency shifting.  

Science.gov (United States)

A laser Doppler velocimeter (LDV) using nonmechanical scanning of multiple points spatially encoded by multichannel serrodyne frequency shifting is proposed for cross-sectional velocity distribution measurement. In the proposed LDV, nonmechanical scanning using wavelength change and simultaneous multipoint measurement using spatial encoding are combined. The use of a LiNbO3 phase-shifter array for multichannel serrodyne modulation makes it possible to simplify the generation of a spatially encoded beam array. An experiment was performed using a sensor probe setup with a six-channel beam array. The results indicate that two-dimensional velocity distribution measurement was successfully demonstrated. PMID:24365841

Maru, Koichi; Watanabe, Kento

2014-01-01

245

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

246

Evaluation of Influence of Acupuncture and Electro-Acupuncture for Blood Perfusion of Stomach by Laser Doppler Blood Perfusion Imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study is to observe effects of acupuncture and electro-acupuncture (EA) on blood perfusion in the stomach, and probe into the application of laser Doppler blood perfusion imaging technique in the study of the effect of acupuncture and moxibustion on the entrails. In the acupuncture group of 20 rats, acupuncture was given at “Zusanli” (ST 36) and in EA group of 18 rats, EA was applied at “Zusanli” (ST 36), with 18 rats without acupuncture used as control group. Ch...

Dong, Zhang; Shun-yue, Li; Shu-you, Wang; Hui-min, Ma

2011-01-01

247

[Functional evaluation of an experimental model of cutaneous microcirculation and pO2 after surgical excision: traditional method vs laser CO2].  

Science.gov (United States)

Within an experimental study project about the interaction between Laser and biological tissues, the authors utilized a Laser Doppler Flowmeter device and a Polarographic method to study the cutaneous microcirculation and the tissue pO2. Under standardized conditions, the experimental model considered the microcirculation measurement and the ptiO2 before and after the exsection of a cutaneous lozenge on the animals back realized with traditional surgical methods (scalpel and electrotome) or with a last generation CO2 Laser in continuous and in pulsed mode. The Laser Doppler Flowmeter showed that the largest perturbation of the microcirculatory flux occurred after the exsection realized with the scalpel and the electrotome. The CO2 Laser utilized in continuous mode showed an influence slightly lower on the microcirculation while in pulsed mode the perturbation was absent. The ptiO2 measurement showed similar results emphasizing that the CO2 surgical Laser technique is less invasive than the traditional. To sum up, these functional methods allowed a careful microcirculation an ptiO2 evaluation and provided useful information about vasal and metabolic alterations, showing that the CO2 surgical Laser utilized in pulsed mode appears to be the less harmful surgical technique for the tissues surrounding the exsection site. PMID:8712609

Morrone, G; Orienti, L; Giavaresi, G; Capelli, S; Fini, M; Rocca, M; Martini, L; Giardino, R

1995-01-01

248

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

2011-05-01

249

Turbine flowmeters the choice for maintenance, verification  

Energy Technology Data Exchange (ETDEWEB)

Sun Pipeline Co. operates as a common-carrier transporter of crude oil, gasoline, home heating oil, diesel fuel, and petrochemicals which are produced and marketed by Sun and several other energy companies. Flow measurement accuracy is crucial to Sun`s ability to adequately service pipeline customers. Sun Pipeline Co. has developed four K factors based on specific service liquids. The four K`s allow them to correct for a specific product`s K factor rather than use less accurate linearizing techniques. The K-factor is the number of output pulses the flowmeter produces per engineering unit of volume throughput. Linear range is the flow range over which the K-factor is constant with the specified limits of linearity. Linearity, the maximum percentage deviation from the K-factor, is stated as a percentage of reading. The repeatability of a flowmeter, the allowable percentage deviation from the stated K-factor, is a measure of the stability of the output under a given set of flow conditions. Repeatability errors of turbine flowmeters are many times smaller than linearity errors. Much greater accuracy is achieved by eliminating dependency of the K-factor by using external linearizing devices.

NONE

1996-07-01

250

Studies of seeding particle velocities in a circular free jet using a laser-Doppler anemometer  

Energy Technology Data Exchange (ETDEWEB)

An experimental study was carried out on the applicability of different drag coefficient models and effective mean diameters of particles to express the velocity slip between seeding particles and air in a free jet. The velocity profiles of the air jet were measured with a laser-Doppler anemometer using titanium dioxide and potato starch as seeding particles. The velocity skip was calculated comparing the measured velocity profiles to the well known solutions of Schlichting. The particle size distribution and the volume median of particles was measured with a Malvern particle analyzer. The measured distribution was then fitted to a loz-normal distribution function when the conversion from volume distribution to area- or number distribution was available. The particle diameter was fitted to the measured velocity slip and particle deceleration data using eight different drag coefficient models. The fitting of particle diameter was done by a software which utilizes a Levenberg-Marquardt non-linear least square fitting algorithm, and finds out the minimum of chi-square value for a given function. The minimum of chi-square value together with the minimum of standard error of fitting was used as a criterion for the goodness-of-fit. The results show that the drag model of Neilson and Gilchrist gives the minimum of chi-square value for both titanium dioxide and potato starch particles. The minimum standard error of fitting was achieved using the drag model of Stokes. The graphical presentation of drag coefficients as a function of Reynolds number of particle shows the difference of these two `best` drag models. The curve fitted diameter of Stokes drag model gives the best results for titanium dioxide particles especially with small Reynolds number of particle, but the drag model of Neilson and Gilchrist gives the best results for potato starch particles. The best fit diameters were compared to the median diameters of the measured particle size distributions and to the mean diameters of the converted log-normal distributions. The best fit diameter (effective mean diameter) of titanium dioxide particles was close to the volume median diameter of the measured size distribution. The best fit diameter of potato starch particles was close to the mean diameter of the converted log-normal number distribution. (orig.) 33 refs.

Saari, K.

1997-12-31

251

Investigation of laser Doppler anemometry in developing a velocity-based measurement technique  

Science.gov (United States)

Acoustic properties, such as the characteristic impedance and the complex propagation constant, of porous materials have been traditionally characterized based on pressure-based measurement techniques using microphones. Although the microphone techniques have evolved since their introduction, the most general form of the microphone technique employs two microphones in characterizing the acoustic field for one continuous medium. The shortcomings of determining the acoustic field based on only two microphones can be overcome by using numerous microphones. However, the use of a number of microphones requires a careful and intricate calibration procedure. This dissertation uses laser Doppler anemometry (LDA) to establish a new measurement technique which can resolve issues that microphone techniques have: First, it is based on a single sensor, thus the calibration is unnecessary when only overall ratio of the acoustic field is required for the characterization of a system. This includes the measurements of the characteristic impedance and the complex propagation constant of a system. Second, it can handle multiple positional measurements without calibrating the signal at each position. Third, it can measure three dimensional components of velocity even in a system with a complex geometry. Fourth, it has a flexible adaptability which is not restricted to a certain type of apparatus only if the apparatus is transparent. LDA is known to possess several disadvantages, such as the requirement of a transparent apparatus, high cost, and necessity of seeding particles. The technique based on LDA combined with a curvefitting algorithm is validated through measurements on three systems. First, the complex propagation constant of the air is measured in a rigidly terminated cylindrical pipe which has very low dissipation. Second, the radiation impedance of an open-ended pipe is measured. These two parameters can be characterized by the ratio of acoustic field measured at multiple locations. Third, the power dissipated in a variable RLC load is measured. The three experiments validate the LDA technique proposed. The utility of the LDA method is then extended to the measurement of the complex propagation constant of the air inside a 100 ppi reticulated vitreous carbon (RVC) sample. Compared to measurements in the available studies, the measurement with the 100 ppi RVC sample supports the LDA technique in that it can achieve a low uncertainty in the determined quantity. This dissertation concludes with using the LDA technique for modal decomposition of the plane wave mode and the (1,1) mode that are driven simultaneously. This modal decomposition suggests that the LDA technique surpasses microphone-based techniques, because they are unable to determine the acoustic field based on an acoustic model with unconfined propagation constants for each modal component.

Jung, Ki Won

252

Decoding carotid pressure waveforms recorded by laser Doppler vibrometry: Effects of rebreathing  

Science.gov (United States)

The principal goal of this study was to assess the capability of the laser Doppler vibrometry (LDV) method for assessing cardiovascular activity. A rebreathing task was used to provoke changes within individuals in cardiac and vascular performance. The rebreathing task is known to produce multiple effects, associated with changes in autonomic drive as well as alterations in blood gases. The rise in CO2 (hypercapnia), in particular, produces changes in the cerebral and systemic circulation. The results from a rebreathing task (involving rebreathing the same air in a rubber bag) are presented for 35 individuals. The LDV pulse was measured from a site overlying the carotid artery. For comparison and validation purposes, several conventional measures of cardiovascular function were also obtained, with an emphasis on the electrocardiogram (ECG), continuous blood pressure (BP) from the radial artery, and measures of myocardial performance using impedance cardiography (ICG). During periods of active rebreathing, ventilation increased. The conventional cardiovascular effects included increased mean arterial BP and systemic vascular resistance, and decreased cardiac stroke volume (SV) and pulse transit time (PTT). These effects were consistent with a pattern of ?-adrenergic stimulation. During the immediate post-rebreathing segments, in contrast, mean BP was largely unaffected but pulse BP increased, as did PTT and SV, whereas systemic vascular resistance decreased-a pattern consistent with ?-adrenergic effects in combination with the direct effects of hypercapnia on the vascular system. Measures of cardiovascular activity derived from the LDV pulse velocity and displacement waveforms revealed patterns of changes that mirrored the results obtained using conventional measures. In particular, the ratio of the maximum early peak in the LDV velocity pulse to the maximum amplitude of the LDV displacement pulse (in an early systolic interval) closely mirrored the conventional SV effects. Additionally, changes in an augmentation ratio (computed as the maximum amplitude of the LDV displacement pulse during systole / amplitude at the end of the incident wave) were very similar to changes in systemic vascular resistance. Heart rates measured from the ECG and LDV were nearly identical. These preliminary results suggest that measures derived using the non-contact LDV technique can provide surrogate measures for those obtained using impedance cardiography.

Casaccia, Sara; Sirevaag, Erik J.; Richter, Edward; O'Sullivan, Joseph A.; Scalise, Lorenzo; Rohrbaugh, John W.

2014-05-01

253

Spatial filtering and proper orthogonal decomposition of scanning laser Doppler vibrometry data for the nondestructive evaluation of frescoes  

Science.gov (United States)

Recently, scanning laser Doppler vibrometry experiments have been conducted in order to identify structural faults in frescoes at the US Capitol. In these experiments, the artwork is subjected to force excitations over a range of frequencies and a laser vibrometer is used to measure the velocity response of the structure over an array of spatial locations. At each frequency, a two-dimensional spatial image of the force-velocity transfer function is obtained. Spatial locations that consistently exhibit large responses are indicative of potential regions of delamination. In this paper the use of proper orthogonal decomposition, also known as principle component analysis, to identify coherent features in the structural response and obtain a succinct representation of the data is described. It is shown that, for the fresco studied in this paper, the response can be characterized in terms of only a few proper orthogonal decomposition modes. Unfortunately, these modes are corrupted by spatially varying noise. This noise is a result of surface irregularities that affect the direction in which the incident laser beam is reflected, which in turn corrupts the measured response at those locations. Therefore, the use of spatial filtering techniques is also explored for removing this "speckle noise" from the measured force-velocity transfer functions prior to performing the proper orthogonal decomposition analysis. Wavelets are particularly well suited for this application because they decompose images into functions that are localized in the spatial and frequency domains. In this paper, several wavelet bases with differing properties are used to filter the scanning laser Doppler vibrometry images. In addition, wavenumber filters, which essentially act as low-pass filters, are also employed. While the results do not definitively show which filtering technique is most effective for this application, it is clear that both wavelet processing and wavenumber filtering can reduce speckle noise while retaining the salient physical features in the image data. Therefore, it is demonstrated that proper orthogonal decomposition analysis coupled with spatial filtering is an effective tool for analyzing scanning laser Doppler vibrometry data in fault detection applications.

Prazenica, Richard J.; Kurdila, Andrew J.; Vignola, Joseph F.

2007-07-01

254

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

255

Hyperfine-structure studies of 139La I by diode-laser-based doppler-free spectroscopy  

International Nuclear Information System (INIS)

Sub-Doppler spectra of 139La I were measured for four transition lines by using saturation absorption spectroscopy. For an atomic excitation laser, we used a single- mode tunable diode laser with a master-oscillator power-amplifer configuration. A La-Ar hollow cathode discharge lamp was used to generate La atomic sources. From the obtained spectra, we determined the hyperfine structure of the upper levels and the hyperfine constants A and B of the 139La isotope. Additionally, when the polarization intermodulated excitation method was adopted, we could observe a decrease of velocity-changing-collision effects in the 675.30 nm transition line of La, compared with the case of saturation absorption spectroscopy

2001-11-01

256

Precise flow rate measurements of natural gas under high pressure with a laser Doppler velocity profile sensor  

Energy Technology Data Exchange (ETDEWEB)

This paper reports about the first application of a laser Doppler velocity profile sensor for precise flow rate measurements of natural gas under high pressure. The profile sensor overcomes the limitations of conventional laser Doppler anemometry (LDA) namely the effect of spatial averaging and the effect of fringe spacing variation (virtual turbulence). It uses two superposed, fan-like interference fringe systems to determine the axial position of a tracer particle inside the LDA's measurement volume. Consequently, a spatial resolution of about 1 {mu}m can be achieved and the effect of virtual turbulence is nearly eliminated. These features predestine the profile sensor for flow rate measurements with high precision. Velocity profile measurements were performed at the German national standard for natural gas, one of the world's leading test facilities for precision flow rate measurements. As a result, the velocity profile of the nozzle flow could be resolved more precisely than with a conventional LDA. Moreover, the measured turbulence intensity of the core flow was of 0.14% mean value and 0.07% minimum value, which is significantly lower than reference measurements with a conventional LDA. The paper describes the performed measurements, gives a discussion and shows possibilities for improvements. As the main result, the goal of 0.1% flow rate uncertainty seems possible by an application of the profile sensor. (orig.)

Buettner, L.; Bayer, C.; Voigt, A.; Czarske, J. [Technische Universitaet Dresden, Faculty of Electrical and Computer Engineering, Professorship for Measuring and Testing Techniques, Dresden (Germany); Mueller, H.; Pape, N.; Strunck, V. [Physikalisch-Technische Bundesanstalt, Department of Gas Flow, Braunschweig (Germany)

2008-12-15

257

Postocclusive reactive hyperemia and postural vasoconstriction in different kinds of leg ulcers--investigations with laser Doppler.  

Science.gov (United States)

Laser-Doppler fluxmetry was performed in 42 patients with leg ulcers (18 venous, 8 arterial, 12 diabetic-arteriolar and 4 mixed arterio-venous) and in 9 healthy controls. Using a bipolar probe measurement was carried out at the ulcer border and on the dorsum of the foot in the supine and in the sitting position. Reactive hyperemia after three minute arterial occlusion was produced in both body-positions. In every ulcer-group resting and peak fluxes showed a statistically significant increase in the ulcer region as compared to normal skin of the lower leg in the control group, the quotient between peak and resting flux ("reactive hyperemia index" RHI) being significantly lower. The RHI values for four ulcer-patients with a dramatic deterioration worsening eight months later were close to one, while the unchanged and improved cases showed median values above 1,2. Sitting up was followed by a decrease of flux in all ulcer-groups as well as in the control group. On the dorsum of the foot there was an increase of the laser Doppler flux in patients with arterial occlusive disease, i.e. in the group with arterial and mixed ulcers. This study shows that the kind of microcirculatory flow damage is not different in various causes of ulcerations. The reduced reactive hyperemic response compared to the increased resting fluxes (amount of RHI-decrease) might be a useful predictor for healing or non-healing of the ulcer. PMID:8310769

Jochmann, W; Mostbeck, A; Partsch, H

1993-01-01

258

Laser Doppler visualisation of the fields of three-dimensional velocity vectors with the help of a minimal number of CCD cameras  

International Nuclear Information System (INIS)

We discuss the possibility of laser Doppler visualisation and measurement of the field of three-dimensional velocity vectors by suppressing the multiparticle scattering influence on the measurement results, when using one CCD camera. The coordinate measuring basis is formed due to switching of the directions and the frequency of spatially combined laser sheets, the frequency being synchronised with the CCD-camera operation. The field of the velocity vectors without the contribution from the multiparticle scattering is produced from the linear combinations of normalised laser sheet images detected with a CCD camera in a frequency-demodulated scattered light. The method can find applications not only in laser diagnostics of gas and condensed media but also in the Doppler spectroscopy of light fields scattered by multiparticle dynamic structures. (laser applications and other topics in quantum electronics)

2010-08-27

259

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.

260

Edge technique for measurement of laser frequency shifts including the Doppler shift  

Science.gov (United States)

A method is disclosed for determining the frequency shift in a laser system by transmitting an outgoing laser beam. An incoming laser beam having a frequency shift is received. A first signal is acquired by transmitting a portion of the incoming laser beam to an energy monitor detector. A second signal is acquired by transmitting a portion of the incoming laser beam through an edge filter to an edge detector, which derives a first normalized signal which is proportional to the transmission of the edge filter at the frequency of the incoming laser beam. A second normalized signal is acquired which is proportional to the transmission of the edge filter at the frequency of the outgoing laser beam. The frequency shift is determined by processing the first and second normalized signals.

Korb, Larry (inventor)

1991-01-01

 
 
 
 
261

Total velocity vector measurements in an axial-flow compressor using a 3-component laser Doppler anemometer  

Science.gov (United States)

A three-color, three-component laser Doppler anemometer (LDA) was used to simultaneously measure the three components of velocity in a low speed (2900 rpm) axial-flow compressor rotor blade passage. Although the mean velocities and entire Reynolds stress tensor were obtained with this system, only the mean velocity results are reported here. It is demonstrated that accurate measurements in the mean motion are possible over much of the blade passage and that the secondary motions can be captured. Confirmation of the observed mean flow results is obtained through a comparison of the three dimensional flow with limited stationary pressure probe measurements and simple irrotational flow assumptions. The presentation of the measurements is followed by a discussion of the difficulties encountered in making three-dimensional velocity measurements in blade passages with LDA and suggestions are made for improving the present system for this task.

Chesnakas, Christopher J.; Dancey, Clinton L.

1988-07-01

262

Developing dual-beam laser Doppler interferometry system for opto-piezoelectric materials based ultrasonic parking sensors and optofluidics sensors  

Science.gov (United States)

Adopting opto-piezoelectric materials, which utilized optical illumination pattern to effect the spatial force distribution induced by piezoelectric materials, to ultrasonic parking sensors and optofluidic chips represent a new research direction in industrial sub-system development. To accommodate performance requirements include wide bandwidth, ultrahigh precision, non-contact measurement mode, linear and angular measurement, etc. associated with the evaluation of the above-mentioned systems, a laser Doppler interferometer was implemented to facilitate the system development. The completely orthogonal alignment design configuration, system performance verified, signal processing algorithms developed as well as the experimental results obtained were all discussed in this paper. Emphasis is on the experimental data obtained from the interferometer and the design changes developed based on the metrology outcome. The system performance improvements induced by the experimental verification achieved by the interferometer were discussed in detail.

Lai, Po-Cheng; Lee, Chih-Kung

2014-03-01

263

Investigation of contact acoustic nonlinearity in delaminations by shearographic imaging, laser doppler vibrometric scanning and finite difference modeling.  

Science.gov (United States)

Full-field dynamic shearography and laser Doppler vibrometric scanning are used to investigate the local contact acoustic nonlinear generation of delamination-induced effects on the vibration of a harmonically excited composite plate containing an artificial defect. Nonlinear elastic behavior caused by the stress-dependent boundary conditions at the delamination interfaces of a circular defect is also simulated by a 3-D second-order, finite-difference, staggered-grid model (displacement-stress formulation). Both the experimental and simulated data reveal an asymmetric motion of the layer above the delamination, which acts as a membrane vibrating with enhanced displacement amplitude around a finite offset displacement. The spectrum of the membrane motion is enriched with clapping-induced harmonics of the excitation frequency. In case of a sufficiently thin and soft membrane, the simulations reveal clear modal behavior at sub-harmonic frequencies caused by inelastic clapping. PMID:20529713

Sarens, Bart; Verstraeten, Bert; Glorieux, Christ; Kalogiannakis, Georgios; Van Hemelrijck, Danny

2010-06-01

264

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

265

Trace isotope analysis using resonance ionization mass spectrometry based on isotope selection with doppler shift of laser ablated atoms  

International Nuclear Information System (INIS)

We have proposed a novel isotope selective Resonance Ionization Mass Spectroscopy (RIMS) concept, which can avoid the Doppler broadening on solid sample direct measurement based on laser ablation technique. We have succeeded in experimentally demonstrating the principle of our RIMS concept. Through comparison between the simulated and experimental results, we have validated the simulation model. It would be concluded from these results that we could achieve the isotope selectivity defined as the ratio of 41Ca to 40Ca sensitivity to be 4.5x1010 by adopting the multi-step excitation scheme in the present method. As future works, we will try to experimentally perform the multi-step excitation scheme and improve the detection efficiency by modifying the ion extraction configuration. (author)

2005-11-01

266

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

267

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

1994-04-01

268

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

269

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)

1991-01-01

270

Self-mixing detection of backscattered radiation in a single-mode erbium fibre laser for Doppler spectroscopy and velocity measurements  

Science.gov (United States)

We report an experimental study of the self-mixing effect in a single-mode multifrequency erbium fibre laser when radiation backscattered from an external moving object arrives at its cavity. To eliminate resulting chaotic pulsations in the laser, we have proposed a technique for suppressing backscattered radiation through the use of multimode fibre for radiation delivery. The multifrequency operation of the laser has been shown to lead to strong fluctuations of the amplitude of the Doppler signal and a nonmonotonic variation of the amplitude with distance to the scattering object. In spite of these features, the self-mixing signal was detected with a high signal-to-noise ratio (above 102) when the radiation was scattered by a rotating disc, and the Doppler frequency shift, evaluated as the centroid of its spectrum, had high stability (0.15%) and linearity relative to the rotation rate. We conclude that the self-mixing effect in this type of fibre laser can be used for measuring the velocity of scattering objects and in Doppler spectroscopy for monitoring the laser evaporation of materials and biological tissues.

Dmitriev, A. K.; Konovalov, A. N.; Ul'yanov, V. A.

2014-04-01

271

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

Science.gov (United States)

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 avoiding any haemorrhagic complication and minimize pain. A total of 20 patients (men, n=13; women, n=7), aged between 6 and 63, were recruited for the procedure. They were affected by chronic hypertrophic tonsillitis with a recurrent fever and other symptoms that were related to oral inflammation. Among the 20 patients, no serious adverse events, including haemorrhage-related complications, were observed. Treatment was well tolerated, even in patients displaying an overall low pain threshold. No dropout or uncompleted procedure occurred in the present study. Minor complications included sore throat, moderate oedema, mild acute pharynx inflammation, slight peritonsillar exudate and local burning. The postoperative pain, measured by Scott-Huskisson visual analogue scale, was between 5 and 40 mm and was easily counteracted by means of external ice packages and nonsteroidal anti-inflammatory drugs, according to the individual patient's need. During the 12-36-month follow-up patients showed improved symptoms (n=7) and complete recovery (n=13). A relapse episode was observed in two patients. This study supports fibre optic laser neodymium-YAG tonsil surgery, named "cribriform intracapsular tonsillectomy" or "Swiss-cheese laser tonsillectomy", as an effective alternative to the traditional cold knife approach or electrosurgery. This approach could become the gold standard for tonsil surgery in the third millennium for safety reasons, acceptable cost-benefit ratio, the precise targeting of the beam across the affected tissues and the short- and long-term recovery. PMID:22855380

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

2013-05-01

272

Differential doppler heterodyning technique  

DEFF Research Database (Denmark)

Measuring velocity without disturbing the moving object is possible by use of the laser doppler heterodyning technique. Theoretical considerations on the doppler shift show that the antenna property of the photodetector can solve an apparent conflict between two different ways of calculating the detected doppler frequency. It is found that the doppler frequency for this particular setup is independent of the direction of detection. Investigations of the signal-to-noise ratio (SNR) show that the maximum SNR-considering the optical setup-is obtained by measuring the frequency difference between two doppler-shifted beams rather than by measuring the shift of a single beam by comparing it with a reference beam. Measurements seem to be in agreement with the theoretical consideration

Lading, Lars

1971-01-01

273

A remote and non-contact method for obtaining the blood-pulse waveform with a laser Doppler vibrometer  

Science.gov (United States)

The use of lasers to remotely and non-invasively detect the blood pressure waveform of humans and animals would provide a powerful diagnostic tool. Current blood pressure measurement tools, such as a cuff, are not useful for burn and trauma victims, and animals require catheterization to acquire accurate blood pressure information. The purpose of our sensor method and apparatus invention is to remotely and non-invasively detect the blood pulse waveform of both animals and humans. This device is used to monitor an animal or human's skin in proximity to an artery using radiation from a laser Doppler vibrometer (LDV). This system measures the velocity (or displacement) of the pulsatile motion of the skin, indicative of physiological parameters of the arterial motion in relation to the cardiac cycle. Tests have been conducted that measures surface velocity with an LDV and a signal-processing unit, with enhanced detection obtained with optional hardware including a retro-reflector dot. The blood pulse waveform is obtained by integrating the velocity signal to get surface displacement using standard signal processing techniques. Continuous recording of the blood pulse waveform yields data containing information on cardiac health and can be analyzed to identify important events in the cardiac cycle, such as heart rate, the timing of peak systole, left ventricular ejection time and aortic valve closure. Experimental results are provided that demonstrates the current capabilities of the optical, non-contact sensor for the continuous, non-contact recording of the blood pulse waveform without causing patient distress.

Desjardins, Candida L.; Antonelli, Lynn T.; Soares, Edward

2007-03-01

274

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

275

Design and analysis of flow rectifier of gas turbine flowmeter  

Directory of Open Access Journals (Sweden)

Full Text Available Three-dimensional computational model for a gas turbine flowmeter is proposed, and the finite volume based SIMPLEC method and k-? turbulence model are used to obtain the detailed information of flow field in turbine flowmeter, such as velocity and pressure distribution. Comparison between numerical results and experimental data reveals a good agreement. A rectifier with little pressure loss is optimally designed and validated numerically and experimentally.

Li Zhi-Fei

2013-01-01

276

Status of the Recent Magnetic Flowmeters  

International Nuclear Information System (INIS)

In order to get the economic benefits and safety of a process facility, 4 major variables - temperature, pressure, level and - should be measured correctly and precisely. The function and performance of recent measuring instruments for the above variables have become sophisticated according to the development of mechanical materials, electronic materials, electronic components such as microprocessors etc. As thermal power of NPP is calculated from the measurement of feedwater temperature and feedwater flowrate, the precise measurement of them could prevent the overpower accident in advance and minimize the power loss. The thermal power margin of US NPP has been guided at 2% by US NRC and NPP electric companies can increase yhe thermal power more than 1% with the use of more advanced instrumentation through the revision of 10 CFR 50 app. k. This report describes general flow measurement technology and the state-of-the art for magnetic flowmeters

2004-01-01

277

Sub-Doppler temperature measurements of laser-cooled atoms using optical nanofibres  

Science.gov (United States)

We present a method for measuring the average temperature of a cloud of cold 85Rb atoms in a magneto-optical trap using an optical nanofibre. A periodic spatial variation is applied to the magnetic fields generated by the trapping coils and this causes the trap centre to oscillate, which, in turn, causes the cloud of cold atoms to oscillate. The optical nanofibre is used to collect the fluorescence emitted by the cold atoms, and the frequency response between the motion of the centre of the oscillating trap and the cloud of atoms is determined. This allows us to make measurements of cloud temperature both above and below the Doppler limit, thereby paving the way for nanofibres to be integrated with ultracold atoms for hybrid quantum devices.

Russell, Laura; Deasy, Kieran; Daly, Mark J.; Morrissey, Michael J.; Chormaic, Síle Nic

2012-01-01

278

Full-field laser Doppler blood-flow imaging and monitoring using an intelligent CMOS camera and area illumination (Invited Paper)  

Science.gov (United States)

An apparatus for parallel, full-field, laser Doppler perfusion imaging has been developed and applied for measurements of blood flow in human skin. This new imaging system allows obtaining 2D flow maps or to monitor flux signals from a plurality of separate predetermined points simultaneously with a 2D matrix of photodetectors. The uniform area illumination is achieved with a highly multimode optical fiber. The detection part of the system is based on an intelligent CMOS camera (iMVS-155) with a built-in digital signal processor. The imaging time of the system is 4 times quicker than for conventional scanning laser Doppler imager. The performance of the system was tested on artificial samples demonstrating linear response to the velocity up to 3 mm/sec. Also, the results of the measurements obtained with the new system on human skin are reported.

Serov, A.; Steinacher, B.; Lasser, T.

2005-06-01

279

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.)

1975-01-01

280

Impurity detection in the APEX tokamak by in-situ doppler shift laser fluorescence spectroscopy  

International Nuclear Information System (INIS)

Laser fluorescence spectroscopy (LFS) is a promising impurity atoms generated from surfaces exposed to fusion plasmas. Here the first continuous wave laser fluorescene measurement of impurities generated during a single tokamak pulse is reported. The results point out the promise of LFS as an essentially real time, in-situ diagnostic allowing a detailed comparison of impurity generation and transport with Tokamak parameters and operating conditions. Results presented will include the Zr-atom density and velocity distribution produced from a Zr-metal target during an Apex Tokamak discharge

1981-10-29

 
 
 
 
281

High-accuracy fuel flowmeter. Phase 2C and 3: The mass flow-rate calibration of high-accuracy fuel flowmeters. Final Report  

Energy Technology Data Exchange (ETDEWEB)

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.W.

1992-02-01

282

Physical model experiment for wave field measurements by means of laser Doppler vibrometer. Measurement of three components; Laser Doppler shindokei ni yoru butsuri model jikken. Hado sanseibun no kenshutsu  

Energy Technology Data Exchange (ETDEWEB)

In this experiment, a beam incident from an oblique direction is reflected by a spherical lens toward the direction of incidence. When the surface of a matter is vibrated by elastic waves, the spherical lens comes into a translation motion that accompanies the vibration. It follows accordingly that the vibration on the surface of the matter may be detected by sensing the spherical lens travelling speed. Three components of the vibration may be determined if beams are focused at one spot from three directions. Detection of the S-wave component by LDV (laser Doppler vibrometer) discloses the complicated wave field in a heterogeneous material, and this physical model experiment may be utilized in various fields of study. For instance, information about problems that may surface in the field work may be collected beforehand in a physical model experiment for developing an S-wave-aided probing method. For the study of seismic wave propagation in a complicated three-dimensional ground structure, a numerical model is not enough, and a physical model experiment will be an effective method to fulfill the purpose. In the monitoring of cracks in a rock, again, not only elastic wave velocity but also waveform information collected from a physical model experiment should be fully utilized. 6 refs., 6 figs.

Nishizawa, O.; Sato, T. [Geological Survey of Japan, Tsukuba (Japan); Lei, X. [DIA Consultant Co. Ltd., Tokyo (Japan)

1997-05-27

283

Use of the Laser-Doppler-Anemometry for the measurement of velocity distributions at the intake of a longitudinal flow heat exchanger  

International Nuclear Information System (INIS)

The Laser-Doppler-Anemometry (LDA) is an optical technic to measure flow velocities. In this report the principles of this method as well as the LDA-system components are described. Especially the signal-processing and the special conditions of use are discussed. The measurement of a two-dimensional velocity distribution at the intake of a longitudinal flow heat exchanger is shown in this investigation. (orig.)

1986-01-01

284

Assessment of the Effects of Low-Level Laser Therapy on the Thyroid Vascularization of Patients with Autoimmune Hypothyroidism by Color Doppler Ultrasound  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background. Chronic autoimmune thyroiditis (CAT) frequently alters thyroid vascularization, likely as a result of the autoimmune process. Objective. To evaluate the effects of low-level laser therapy (LLLT) on the thyroid vascularization of patients with hypothyroidism induced by CAT using color Doppler ultrasound parameters. Methods. In this randomized clinical trial, 43 patients who underwent levothyroxine replacement for CAT-induced hypothyroidism were randomly assigned to receive either 1...

Ho?fling, Danilo Bianchini; Chavantes, Maria Cristina; Juliano, Adriana G.; Cerri, Giovanni G.; Knobel, Meyer; Yoshimura, Elisabeth M.; Chammas, Maria Cristina

2012-01-01

285

Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in laser-cooled fermionic isotopes of neutral mercury  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have performed for the first time direct laser spectroscopy of the 1S0-3P0 optical clock transition at 265.6 nm in fermionic isotopes of neutral mercury laser-cooled in a magneto-optical trap. Spectroscopy is performed by measuring the depletion of the magneto-optical trap induced by the excitation of the long-lived 3P0 state by a probe at 265.6 nm. Measurements resolve the Doppler-free recoil doublet allowing for a determination of the transition frequency to an uncer- tainty well below t...

2008-01-01

286

Application of CFD to Explain Anomalous Stall Behavior of the SSME Flowmeter  

Science.gov (United States)

The Space Shuttle Main Engine (SSME) Fuel Flowmeter is located in the duct between the low and high pressure fuel turbopumps. In the flowmeter the rotation rate of a 4-blade rotor positioned downstream of two flow straighteners is employed to measure the engine fuel flow rate and thereby control the engine mixture ratio via the engine controller. Hence, inaccurate operation of the flowmeter could have serious consequences for SSME engine operation and performance, forcing, for example, tanking of extra fuel to allow for inaccurate flowmeter measurement. Since the current flight flowmeter configuration was incorporated into the SSME in the early eighties, some anomalies in flowmeter behavior have been observed. The initial flowmeter incorporated an "egg crate" design for the two flow straighteners which turn the duct flow to make it more uniform and parallel after it has come out of the 90 degree bend just upstream of the flowmeter.

Ascoli, E.; Clever, W.; Hadid, A.; Lynch, E. D.; Stewart, M.; Lee, K.

1999-01-01

287

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

288

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

Science.gov (United States)

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; Mahé, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Abraham, Pierre

2010-10-01

289

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)

1986-01-01

290

Laser Doppler flowmetry detection of endothelial dysfunction in end-stage renal disease patients: correlation with cardiovascular risk.  

Science.gov (United States)

Prediction of cardiovascular (CV) complications represents the Achilles' heel of end-stage renal disease. Surrogate markers of endothelial dysfunction have been advocated as predictors of CV risk in this cohort of patients. We have recently adapted a noninvasive laser Doppler flowmetry (LDF) functional testing of endothelium-dependent microvascular reactivity and demonstrated that end-stage renal disease patients are characterized by profound alterations in thermal hyperemic responsiveness. We hypothesized that such functional assessment of the cutaneous microcirculation may offer a valid, noninvasive test of the severity of endothelial dysfunction and CV risk. To test this hypothesis, we performed a cross-sectional study, in which we compared LDF measurements to conventional risk factors, and performed a pilot longitudinal study. LDF studies were performed in 70 patients and 33 controls. Framingham and Cardiorisk scores were near equivalent for low-risk patients, but more divergent as risk increased. C reactive protein (CRP) levels and LDF parameters (amplitude of thermal hyperemia (TH), area under the curve of TH) showed significant abnormality in high-risk vs low-risk patients calculated using either Framingham or Cardiorisk scores. Patients who had abnormal LDF parameters showed increased CV mortality, however, had similar risk assessments (Framingham, Cardiorisk, CRP, and homocysteine) to those with unimpaired LDF tracings. In conclusion, LDF parameters of microvascular reactivity offer a sensitive characterization of endothelial dysfunction, which may improve CV risk assessment through incorporation into the Framingham or Cardiorisk algorithm. PMID:16710351

Kruger, A; Stewart, J; Sahityani, R; O'Riordan, E; Thompson, C; Adler, S; Garrick, R; Vallance, P; Goligorsky, M S

2006-07-01

291

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)

2013-06-28

292

Heterodyne laser Doppler distance sensor with phase coding measuring stationary as well as laterally and axially moving objects  

International Nuclear Information System (INIS)

Both in production engineering and process control, multidirectional displacements, deformations and vibrations of moving or rotating components have to be measured dynamically, contactlessly and with high precision. Optical sensors would be predestined for this task, but their measurement rate is often fundamentally limited. Furthermore, almost all conventional sensors measure only one measurand, i.e. either out-of-plane or in-plane distance or velocity. To solve this problem, we present a novel phase coded heterodyne laser Doppler distance sensor (PH-LDDS), which is able to determine out-of-plane (axial) position and in-plane (lateral) velocity of rough solid-state objects simultaneously and independently with a single sensor. Due to the applied heterodyne technique, stationary or purely axially moving objects can also be measured. In addition, it is shown theoretically as well as experimentally that this sensor offers concurrently high temporal resolution and high position resolution since its position uncertainty is in principle independent of the lateral object velocity in contrast to conventional distance sensors. This is a unique feature of the PH-LDDS enabling precise and dynamic position and shape measurements also of fast moving objects. With an optimized sensor setup, an average position resolution of 240 nm was obtained

2010-02-01

293

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.

294

Hemodynamic changes during neural deactivation in awake mice: a measurement by laser-Doppler flowmetry in crossed cerebellar diaschisis.  

Science.gov (United States)

Crossed cerebellar diaschisis (CCD) caused by contralateral supratentorial lesions can be considered a condition of neural deactivation, and hemodynamic changes in CCD were investigated with positron emission tomography (PET) in humans. In the present study, to investigate the effects of neural deactivation on hemodynamics, we developed a new mouse model of CCD, which was caused by middle cerebral artery occlusion (MCAO), and measured changes in cerebellar blood flow (CbBF), red blood cell (RBC) velocity and concentration due to CCD using laser-Doppler flowmetry (LDF) in awake mice. The ratio of the CCD side to the unaffected side in the cerebellum for CbBF 1 day after MCAO was decreased by -18% compared to baseline (before CCD). The ratio of the CCD side to the unaffected side for RBC concentration 1 day after MCAO was decreased by -23% compared to baseline. However, no significant changes in the ratio of the CCD side to the unaffected side were observed for RBC velocity. The present results indicate that the reduction of CbBF induced by neural deactivation was mainly caused by the decrease in RBC concentration. In contrast, our previous study showed that RBC velocity had a dominant role in the increase in cerebral blood flow (CBF) induced by neural activation. If RBC concentration can be considered an indicator of cerebral blood volume (CBV), hemodynamic changes due to neural activation and deactivation measured by LDF in mice might be in good agreement with human PET studies. PMID:24076448

Takuwa, Hiroyuki; Tajima, Yosuke; Kokuryo, Daisuke; Matsuura, Tetsuya; Kawaguchi, Hiroshi; Masamoto, Kazuto; Taniguchi, Junko; Ikoma, Yoko; Seki, Chie; Aoki, Ichio; Tomita, Yutaka; Suzuki, Norihiro; Kanno, Iwao; Ito, Hiroshi

2013-11-01

295

Interpretation of spray behavior in complex aerodynamic flows using phase Doppler interferometry and planar liquid laser induced fluorescence  

Energy Technology Data Exchange (ETDEWEB)

The increasing need to mitigate pollutants produced by liquid fired combustion systems is leading to critical assessment of current systems in an effort to sufficiently refine them. These systems typically feature complex aerodynamic flows which serve to stabilize the reaction and are often the result of years of trial and error testing. In order to advance current systems suitable for future environmentally sensitive applications, basic understanding of the processes occurring is required. Recent developments in optical diagnostic techniques are providing the opportunity to attain such understanding. The present work applies a relatively well established technique (phase Doppler interferometry--PDI) to study the complex behavior of two-phase flows. PDI provides a wealth of information about the droplet size and velocity distributions as well as droplet concentration at discrete points within the flow. In addition, a relatively new technique (planar liquid laser induced fluorescence--PLLIF) is applied in order to extend the understanding of the structure of the flow. The PLLIF technique provides, in principle, the spatial distribution of liquid mass within a plane through the spray. This information is important because, in combustion systems, the homogeneity of the spatial distribution of fuel can play a significant role in the formation of pollutants. The results demonstrate the utility and potential limitations of the PLLIF technique. In addition, basic understanding of the complex flow structure is provided by combining the results from the two techniques.

McDonell, V.; Lee, S.; Samuelsen, S. [Univ. of California, Irvine, CA (United States). UCI Combustion Lab.

1995-12-31

296

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

297

Doppler Lidar (DL) Handbook  

Energy Technology Data Exchange (ETDEWEB)

The Doppler lidar (DL) is an active remote sensing instrument that provides range- and time-resolved measurements of radial velocity and attenuated backscatter. The principle of operation is similar to radar in that pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is inferred. The radial or line-of-sight velocity of the scatterers is determined from the Doppler frequency shift of the backscattered radiation. The DL uses a heterodyne detection technique in which the return signal is mixed with a reference laser beam (i.e., local oscillator) of known frequency. An onboard signal processing computer then determines the Doppler frequency shift from the spectra of the heterodyne signal. The energy content of the Doppler spectra can also be used to determine attenuated backscatter.

Newsom, RK

2012-02-13

298

Doppler Effect  

Science.gov (United States)

Doppler effect followed from water waves to sound waves to light waves. Red shift of the universe is also explored. What is doppler effect? It is the change in frequency of a wave for an observer moving relative to the source of the wave. What does that mean? Watch this: moving doppler effect video What does the doppler effect look like in a stationary and moving object? dooppler effect views What does doppler effect have to do with stars and galaxies??? View the following ...

Brown, Mrs.

2010-10-26

299

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

300

Improve flowmeter accuracy in cramped quarters  

International Nuclear Information System (INIS)

Getting accurate pipeline flow measurements with an orifice meter requires that the flow be streamlined and stable upstream of the orifice. A long, straight section of pipe usually provides the required stability. However, in many cases, a complex piping configuration or cramped site conditions make such long, straight piping runs more of a luxury than the norm. Straightening devices such as honeycombs and vanes inserted upstream of the orifice can reduce the length of straight pipe required. But they provide only marginal improvements in measurement accuracy, and may still require significant straight pipe. A new flow-conditioning device developed by Cheng Fluid Systems, Inc. (Sunnyvale, Calif.) solves this problem. Combining rotation vanes with a 90-deg elbow, the Cheng Rotational Vane (CRV) produces stable flow immediately downstream of the elbow. A complex gas piping system at Bechtel Savannah River, Inc.'s Defense Waste Processing Facility (DWPF; Aiken, S.C.) contains several 90-deg, long-radius elbows. Located in a high-radiation zone, the pipe carries offgas from a glass melter. During operation, impulse lines transmit the pressure drop signal outside the radiation area, where a microprocessor converts it to a 4- to 20-mA signal. That signal is then sent to a remote monitoring and control system. With the new Cheng elbow vanes in place, the orifice flowmeter has performed to design capacity. And, to date, the system has shown no random fluctuations and no lack of repeatability

1996-03-01

 
 
 
 
301

Factors affecting the performance of ultrasonic flowmeters  

Energy Technology Data Exchange (ETDEWEB)

A programme of work is currently underway at NEL to investigate and characterise the performance of liquid ultrasonic meters over a wide range of conditions. This paper presents the results of laboratory evaluations in addition to the initial results of combined flow and flowmeter modelling. Two-phase, oil/gas performance tests were conducted on commercially available meters of 4-inch nominal bore. Specific results have been selected to illustrate performance variations related to factors in meter design and operation. Two-phase, oil/water performance tests with water-cuts of up to 15 % were also conducted on the above meters. These results are presented in their entirety. The results show deviations from single-phase performance which vary for each meter design. Baseline calibration results for four commercially available clamp-on meters are presented. The results were obtained in good installation conditions on stainless steel pipes of 4-inch and 8-inch nominal bore. The results show different levels of accuracy associated with each meter and a general conformation with predicted behaviour. The final section of the paper presents results obtained by a systematic numerical method of determining the flow profile sensitivity of various meter configurations. The results provide quantitative confirmation of the reduced sensitivity of multipath designs to variations in the velocity profile. (author)

Brown, G.J.

1997-07-01

302

Proof of principle of a nuclear turbine flowmeter  

Energy Technology Data Exchange (ETDEWEB)

The potentiality of a new type of flowmeter, intended to measure the coolant flow rate through a fuel assembly of a nuclear reactor, was investigated. This new type of flowmeter, the nuclear turbine flowmeter, has the advantage that no extra signal wires are needed; the signal can be read by a neutron detector positioned in its vicinity. The influence of a rotating test turbine (installed in a setup at the Hoger Onderwijs Reactor in Delft, The Netherlands) on the signals of several neutron detectors was analyzed. From the results, it appeared that the rotation frequency of the test turbine could easily be detected by all neutron detectors used. The influence of the rotating test turbine on the signals of detectors positioned nearby is strong compared with the background noise level found for in-core neutron detectors in boiling water reactors.

Van Der Hagen, T.H.J.J. (Delft Univ. of Technology (Netherlands))

1993-05-01

303

Study on the development of ultrasonic gas flowmeter  

International Nuclear Information System (INIS)

Ultrasonic flowmeters have more advantages than the conventional method using pressure-difference. In these reasons, many advanced nations are already selling the commercial model. In RIST, we have been developed ultrasonic gas flow meter for the localization since a project was been contracted with POSCO in 1997. This paper describes a new ultrasonic gas flowmeter. This ultrasonic gas flowmeter is developed for accurate measurement of gases in a harsh environmental conditions. It is especially suited for measuring LDG, COG, BFG gases produced in iron and steel making process. In this study, we had developed the commercial model about the first tested model and applied a completed system to the POSCO gas line. Its performance has already well been proven by extensive field tests for several months in POSCO, iron and steel making company

2001-06-27

304

Experimental calibration of electromagnetic flowmeters for Pb17Li  

International Nuclear Information System (INIS)

The building of Pb17Li experimental loops made us to develop a flowmeter for the eutectic alloy. The electromagnetic flowmeter type has been chosen due to the experience gained in sodium activities. One should have a reliable 'flexible' calibration system in order to assure the initial calibration of the flowmeters and the possibility of following checking, made necessary by the changing of the electric conductivity of the duct after use. In the wide operating range of flowrate (940/260 cm3/s) and temperature (350/500deg C) it has been shown that the calibration method is affected by ?±2% total error. A semi-theoretical calibration procedure has been followed as well. Results turned out to be very close to the experimental ones (maximum difference is about 7%). (orig.)

1991-12-01

305

High-rangeability ultrasonic gas flowmeter for monitoring flare gas.  

Science.gov (United States)

A transit-time ultrasonic gas flowmeter for high-rangeability requirements, such as those encountered in flare-gas flow-metering, is presented. The concept of ray rescue angle for the orientation of the ultrasonic transducers in single-beam transit-time ultrasonic flowmeters is introduced to overcome the problem of ultrasonic beam drift in high-velocity flows. To overcome problems associated with noise at high velocities, a chirp signal is used. To preserve the accuracy of the meter at low velocities near zero flow, a combination of chirp and continuous-wave signals is used to interrogate the flow. Overall system performance is presented, based on results from extensive wind-tunnel tests. PMID:18284961

Mylvaganam, K S

1989-01-01

306

High-rangeability ultrasonic gas flowmeter for monitoring flare gas  

Energy Technology Data Exchange (ETDEWEB)

A transit-time ultrasonic gas flowmeter for high-range-ability requirements, such as those encountered in flare-gas flow-metering, is presented. The concept of ray rescue angle for the orientation of the ultrasonic transducers in single-beam transit-time ultrasonic flowmeters is introduced to overcome the problem of ultrasonic beam drift in high-velocity flows. To overcome problems associated with noise at high velocities, use of a chirp signal is presented. To preserve accuracy of the meter at low velocities near zero flow, a combination of chirp and continuous wave (CW) signals is used to interrogate the flow. Overall system performance is presented, based on results from extensive wind-tunnel tests.

Mylvaganam, K.S.

1989-03-01

307

Effects of antipsoriatic treatment on cutaneous blood flow in psoriasis measured by 133Xe washout method and laser Doppler velocimetry  

International Nuclear Information System (INIS)

In 8 patients with psoriasis vulgaris, the cutaneous blood flow (CBF) was measured simultaneously in both involved and uninvolved psoriatic skin before (i.e., on the first day of hospitalization) and on the 3rd, 7th, 14th, and 28th days of treatment with tar. The 133Xe washout method was used after epicutaneous labeling and compared to the laser Doppler velocimetry (LDV) technique. Control experiments were performed in 10 normal individuals. Before treatment the mean CBF in involved psoriatic skin was 62.6 +/- 18.7 SD ml X (100 g X min)-1, which is significantly higher than CBF of uninvolved skin in psoriatic patients, 9.5 +/- 4.0 SD ml X (100 g X min)-1, (p less than 0.01) and is 13.6 times higher than CBF in the normal individuals (p less than 0.01). Fifty hours following onset of treatment (i.e., after only 2 applications of tar), mean CBF of the involved psoriatic skin had decreased significantly to 35.0 +/- 13.9 SD ml X (100 g X min)-1, (p less than 0.01), which was not statistically different from the CBF on the 7th day. During the following weeks, the CBF in involved psoriatic skin decreased at a more moderate rate than that observed during the first week and was 15.0 +/- 6.1 SD ml X (100 g X min)-1 on the 28th day. This value is not significantly different from the CBF of uninvolved skin in these patients. At the end of treatment, the CBF of the uninvolved skin had decreased significantly (p less than 0.05) in all the patients to values similar to those observed in the skin of normal individuals. A parallel decline was observed in a clinical psoriatic score index; however, it is not known whether the observed decrease in CBF was preceded or succeeded by the clinical improvement

1985-01-01

308

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 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

2008-12-01

309

Nailfold capillaroscopy and blood flow laser-doppler analysis of the microvascular damage in systemic sclerosis: preliminary results  

Directory of Open Access Journals (Sweden)

Full Text Available Objectives: Systemic sclerosis (SSc is characterized by altered microvascular structure and function. Nailfold videocapillaroscopy (NVC is the tool to evaluate capillary morphological structure and laser-Doppler Blood flowmetry (LDF can be used to estimate cutaneous blood flow of microvessels. The aim of this study was to investigate possible relationships between capillary morphology and blood flow in SSc. Methods: 27 SSc patients and 12 healthy subjects were enrolled. SSc microvascular involvement, as evaluated by NVC, was classified in three different patterns (“Early”, “Active”, “Late”. LDF analysis was performed at the II, III, IV, V hand fingers in both hands and both at cutaneous temperature and at 36°C. Statistical evaluation was carried out by non-parametric procedures. Results: Blood flow was found significantly lower in SSc patients when compared with healthy subjects (p<0.05. The heating of the probe to 36°C induced a significant increase in peripheral blood flow in all subjects compared to baseline (p <0.05, however, the amount of variation was significantly lower in patients with SSc, compared with healthy controls (p <0.05. The SSc patients with NVC “Late” pattern, showed lower values of peripheral blood flow than patients with NVC “Active” or “Early” patterns (p<0.05. Moreover, a negative correlation between the tissue perfusion score and the progression of the SSc microangiopathy was observed, as well as between the tissue perfusion and the duration of the Raynaud’s phenomenon (p <0.03. Conclusions: LDF can be employed to evaluate blood perfusion in the microvascular circulation in SSc patients. The blood flow changes observed with the LDF seem to correlate with the severity of microvascular damage in SSc as detected by NVC.

C. Pizzorni

2011-06-01

310

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

Energy Technology Data Exchange (ETDEWEB)

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 {phi} 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 [{phi}{sub 0}-{delta}{phi}/2,{phi}{sub 0}+{delta}{phi}/2] in order to obtain mean velocities and turbulence values for an angular position {phi}{sub 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 et al. 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 {delta}{phi} 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. (orig.)

Glas, W.; Forstner, M.; Kuhn, K.; Jaberg, H. [TU Graz (Austria). Inst. fur Hydraulische Stroemungsmaschinen

2000-11-01

311

Experimental analysis of turbulent flow in a rectangular duct with arrays of blocks by using laser-doppler velocimeter  

International Nuclear Information System (INIS)

An experimental study of developing flow in a rectangular duct with arrays of blocks was carried out at the Reynolds number of 3.26x104 by using a Laser-Doppler velocimeter. The total amount of ten blocks are staggered each other and upstream tangent with rectangular cross section are set to obtain fully developed turbulent flow. The test section duct with blocks was placed at distance of 40.5 times hydraulic diameter from the duct inlet. Three components of mean velocity and the five components of the six Reynolds stresses were measured at nine different locations to clarify the development of turbulent structure. The measurement has been performed in the flow region between number 7 and number 8 blocks. As a result of this experimental study, it was pointed out as a characteristic feature that the two peaks of stream-wise velocity were generated in the central and wall side regions respectively. The measurements of secondary flow vectors suggest that this phenomenon is caused by transforming lower velocity fluid to upward of block from leading edge of block and the large values of secondary flow, which reach maximum percentage of 50% for mean bulk velocity, are produced at leading edge and wake region of block. Adding to this, separated and reattached flows are observed in wake region of blocks and the distributions of three normal stresses indicate a strong intensity near the reattachment region. The distributions of Reynolds shear stress show the opposite sign region, which is owing to streamwise velocity distorted by secondary flow. (author)

2002-06-01

312

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

313

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

314

Modelling of flow in pipes and ultrasonic flowmeter bodies  

Directory of Open Access Journals (Sweden)

Full Text Available The contribution gives a summary of the flow modelling in flow parts of ultrasonic flowmeters using CFD system ANSYS/FLUENT. The article describes the basic techniques used to create CFD models of flow parts flow and selected results of the flow fields. The first part of the article summarizes the results of velocity profiles in smooth pipes for various turbulent models and used relations. The second part describes selected results of the numerical modelling of flow in the flow parts of the ultrasonic flowmeters and their partially comparison with experimental results.

Matas Richard

2014-03-01

315

Modelling of flow in pipes and ultrasonic flowmeter bodies  

Science.gov (United States)

The contribution gives a summary of the flow modelling in flow parts of ultrasonic flowmeters using CFD system ANSYS/FLUENT. The article describes the basic techniques used to create CFD models of flow parts flow and selected results of the flow fields. The first part of the article summarizes the results of velocity profiles in smooth pipes for various turbulent models and used relations. The second part describes selected results of the numerical modelling of flow in the flow parts of the ultrasonic flowmeters and their partially comparison with experimental results.

Matas, Richard; Cibera, Vaclav; Syka, Tomas

2014-03-01

316

FLOWCER - a flowmeter based on radiotracer techniques  

International Nuclear Information System (INIS)

One of the most difficult problems in the field of flow measurement is the lack of a portable, clamp-on type of flowmeter of good accuracy. This is a serious restriction in non-continuous flow measurements and on-site calibrations of flow meters. One possibility of constructing a meter capable for these measurements is to use tracer techniques, particularly radioisotope tracers. A flow measurement instrument, FLOWCER, has been developed in the Reactor Laboratory of the Technical Research Centre of Finland (VTT). The instrument is based on the radioisotope transit time method. The device can be used for the accurate instantaneous measurement of volume flow rate in ducts. The tracer used is "1"3"7"mBa produced in a portable isotope generator. Because of the short half-life (2.6 min) of "1"3"7"mBa the measurement is radiologically very safe. The device consists of the isotope generator, an injection device for the tracer, radiation detectors, a data logger unit and a micro-computer. Also a transducer for various other quantities than flow may be connected to the analog input channels of the FLOWCER. The measurement program can be modified for measurements of different types. The FLOWCER has been used for the measurememts of energy and material balances, for the on-site calibrations of flow meters and for pump efficiency analysis. The application most frequently used has been the on-site calibration of flow meters. According to the present experience (over 100 calibrated flow meters) the accuracy level of flow measurements can be increased by a factor of ten or more by using the transit time method for on-site calibration

1986-01-01

317

Vascularity in cutaneous melanoma detected by Doppler sonography and histology: correlation with tumour behaviour.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The blood flow in 71 primary skin melanomas was investigated by a 10MHz Doppler ultrasound flowmeter and flow signals were analysed on an Angioscan-II spectrum analyser. Doppler flow signals were detected in 44 tumours, with a close relationship to Breslow's tumour thickness. No blood flow signal was detected in 27 lesions and 25 of these had a tumour thickness of 0.8 mm or less. Ninety-seven per cent of tumours of thickness greater than 0.8 mm had detectable Doppler flow signals. Histologica...

Srivastava, A.; Hughes, L. E.; Woodcock, J. P.; Laidler, P.

1989-01-01

318

Doppler Shift Methods for Plasma Diagnostics,  

Science.gov (United States)

Work to develop novel advanced laser spectroscopy plasma diagnostic methods is described. The methods are based on observing the doppler shift in the absorption liners of ionic species. Two methods under study are Velocity Modulated Laser Spectroscopy and...

M. Sassi J. W. Daily

1987-01-01

319

Performance of turbine-type flowmeters in liquid hydrogen  

Science.gov (United States)

Tests using commercially available flowmeters provide information on the constancy in water of the calibration factor /pulses per unit volume/, on the maximum deviation of the factor from its mean value, and on the probability of predicting the calibration factor of a meter in liquid hydrogen at full scale.

1967-01-01

320

The Q-sonic ultrasonic gas flowmeter for custody transfer  

Energy Technology Data Exchange (ETDEWEB)

This paper presents an outline of the theory and methods applied in ultrasonic gas flow metering for custody transfer. The development of a multipath instrument for custody transfer will be discussed, and recent developments will be indicated. Practical applications are illustrated using the Servex 5-path Q.Sonic custody transfer flowmeter.

Drenthen, J.G. [Stork Servex B.V., Dordrecht (Netherlands)

1995-12-31

 
 
 
 
321

Doppler Effect  

Science.gov (United States)

In this activity, learners use a tuning fork to explore how the Doppler effect works. They strike the tuning fork to produce a sound, then observe as the tone changes as the fork is swung back and forth. Learners also explore applications of the Doppler effect in technology.

Cosi

2009-01-01

322

Free Convection of Gases in a Horizontal Cylinder with Differentially Heated End Walls - a Study by Laser Doppler Anemometry.  

Science.gov (United States)

An understanding of the prevailing fluid dynamics in ampoules used for the growth of single crystals from the vapor is mandatory for the design of growth apparatus and processes. In addition to diffusion in chemical concentration gradients, convective flows such as Stefan flow, streaming, and expansive and solutal convection can significantly affect transport rates, homogeneity, and morphological stability. Expansive convection dominates in many actual crystal growth situations. Its experimental characterization and mathematical description are the objectives of this dissertation. Therefore, the free convective flow of gases in a horizontal cylinder (radius to length, r(,0)/L = 0.1) with different end temperatures was characterized by Laser Doppler Anemometry (LDA). A linear temperature gradient at the wall of the quartz glass enclosure was established with a novel radiation heating arrangement. Experiments were conducted over a wide range of the Rayleigh number (74 (LESSTHEQ) Ra (LESSTHEQ) 1.3(.)10('6), with Ra (PROPORTIONAL) r(,0)('3)), which was varied via gas species and gas pressure. Agreement with theoretical predictions was found for velocity profiles in the cylinder core region at low Ra, and in the end regions at high Ra. A special effort was made to characterize the 3D flow behavior in the end zones. It was found that only part of the fluid flows along the cold (hot) thermode into the lower (upper) half of the cylinder. The remaining part changes the flow direction by dropping (rising) at the side wall over a considerable distance from the respective thermode. Nusselt numbers were estimated for a horizontal cylinder with adiabatic wall at high Rayleigh numbers, in good agreement with experiments of Kimura and Bejan. The calculations were based on the experimental finding that Gill's theory for free convection in tall, rectangular enclosures also predicts the velocity profile at mid-height near the vertical end walls in a long cylinder. Complete thermal stratification was assumed. This simple model yields more realistic Nusselt numbers for systems with Prandtl number (GREATERTHEQ) 1 than earlier more complex treatments. Finally, objects simulating crystals were inserted into the cylinder and positioned near the cold thermode. Their influence on the fluid flow was also studied by LDA.

Schiroky, Gerhard Hans

323

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

324

Development and testing of laser Doppler system components for wake vortex monitoring. Volume 1: Scanner development, laboratory and field testing and system modeling  

Science.gov (United States)

A servo-controlled range/elevation scanner for the laser Doppler velocimeter (LDV) was developed and tested in the field to assess its performance in detecting and monitoring aircraft trailing vortices in an airport environment. The elevation scanner provides a capability to manually point the LDV telescope at operator chosen angles from 3.2 deg. to 89.6 deg within 0.2 deg, or to automatically scan the units between operator chosen limits at operator chosen rates of 0.1 Hz to 0.5 Hz. The range scanner provides a capability to manually adjust the focal point of the system from a range of 32 meters to a range of 896 meters under operator control, or to scan between operator chosen limits and at rates from 0.1 Hz to 6.9 Hz. The scanner controls are designed to allow simulataneous range and elevation scanning so as to provide finger scan patterns, arc scan patterns, and vertical line scan patterns. The development and testing of the unit is discussed, along with a fluid dynamic model of the wake vortex developed in a laser Doppler vortex sensor simulation program.

Wilson, D. J.; Krause, M. C.; Coffey, E. W.; Huang, C. C.; Edwards, B. B.; Shrider, K. R.; Jetton, J. L.; Morrison, L. K.

1974-01-01

325

Parameter optimization for Doppler laser cooling of a low-energy heavy ion beam at the storage ring S-LSR  

Science.gov (United States)

S-LSR is a compact ion storage ring constructed at Kyoto University several years ago. The ring is equipped with a Doppler laser cooling system aimed at beam crystallization. Bearing in mind hardware limitations in S-LSR, we try to find an optimum set of primary experimental parameters for the production of an ultracold heavy ion beam. Systematic molecular dynamics simulations are carried out for this purpose. It is concluded that the detuning and spot size of the cooling laser should be chosen around -42 MHz and 1.5 mm, respectively, for the most efficient cooling of 40 keV ^{24}Mg^+ beams in S-LSR. Under the optimum conditions, the use of the resonant coupling method followed by radio-frequency field ramping enables us to reach an extremely low beam temperature on the order of 0.1 K in the transverse degrees of freedom. The longitudinal degree of freedom can be cooled to close to the Doppler limit; i.e., to the mK range. We also numerically demonstrate that it is possible to establish a stable, long one-dimensionally ordered state of ions.

Osaki, Kazuya; Okamoto, Hiromi

2014-05-01

326

Doppler echocardiography  

Energy Technology Data Exchange (ETDEWEB)

This text will serve to introduce the use of Doppler in clinical cardiology in a straightforward, practical format. The work features the following categories: a review and discussion of the fundamental principles and characteristics of ultrasound; examination techniques, including continuous and pulse modes; clinical application with acquired disease the focus; congenital disease, particularly defects, stenotic lesions, and complicated lesions; and fetal clinical applications of Doppler echocardiography.

Nanda, N.C.

1985-01-01

327

Doppler echocardiography  

International Nuclear Information System (INIS)

This text will serve to introduce the use of Doppler in clinical cardiology in a straightforward, practical format. The work features the following categories: a review and discussion of the fundamental principles and characteristics of ultrasound; examination techniques, including continuous and pulse modes; clinical application with acquired disease the focus; congenital disease, particularly defects, stenotic lesions, and complicated lesions; and fetal clinical applications of Doppler echocardiography

1985-01-01

328

Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves / Velocimetria laser de escoamento permanente através de duas próteses cardíacas de duplo folheto  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese INTRODUÇÃO: A caracterização hidrodinâmica in vitro de próteses de válvulas cardíacas fornece informações importantes quanto ao seu funcionamento, sobretudo se realizada por meio de métodos não-invasivos de anemometria. Uma vez obtidos os perfis de velocidade para cada válvula, é possível compará-la [...] s quanto ao seu desempenho hidrodinâmico. Neste primeiro estudo experimental de anemometria laser com válvulas mecânicas, as simulações foram realizadas em bancada de testes para escoamento permanente. OBJETIVO: Comparar perfis de velocidade unidimensional no plano central de duas próteses aórticas de duplo folheto St. Jude (modelos AGN 21 - 751 e 21 AJ - 501) submetidas a um regime de fluxo permanente, para quatro seções distintas, três à jusante e uma à montante. MÉTODOS: Proporcionar condições de similaridade para o escoamento através de cada prótese, por meio de bancada hidrodinâmica para escoamento permanente (água, à vazão de 17 L/min.) e, por meio de anemometria laser unidimensional, obter os perfis de velocidades para as mesmas seções e varreduras. RESULTADOS: Verificou-se que as maiores velocidades correspondem à prótese de diâmetro interno menor e que as instabilidades do fluxo são maiores à medida que a seção de interesse encontra-se mais próxima da válvula. Também foram verificadas as regiões de recirculação, de estagnação do fluxo e de baixa pressão, além dos picos de velocidade para o escoamento em questão. CONCLUSÕES: Sob o aspecto hidrodinâmico e para todas as seções de interesse, foi possível concluir a preferência da válvula de modelo AGN 21 - 751 (RegentTM) sobre a 21 AJ - 501 (Master Series). Os resultados obtidos permitiram escolher, para os próximos trabalhos, um foco de estudo mais específico para regiões concretas dessas próteses. Abstract in english INTRODUCTION: In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hy [...] drodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. OBJECTIVE: To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. METHODS: To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min.) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. RESULTS: It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. CONCLUSIONS: Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.

Ovandir, Bazan; Jayme Pinto, Ortiz; Francisco Ubaldo, Vieira Junior; Reinaldo Wilson, Vieira; Nilson, Antunes; Fabio Bittencourt Dutra, Tabacow; Eduardo Tavares, Costa; Orlando, Petrucci Junior.

329

In-sodium test of ultra-sonic flowmeter for fast breeder reactor  

International Nuclear Information System (INIS)

Developments on the ultra-sonic flowmeters, which are used widely in the water loop, have been carried out for the application on the sodium loop in fast breeder reactor. This is because of that ultra-sonic flowmeters have several characteristics needed to the large pipe sodium flowmeter, i.e. good linearity, lightweight, leak tight, low cost etc.. After fundamental improvement about the settling method of transducer to high temperature duct and about measurement circuit were developed, in-water tests were conducted and effectiveness of such improvements were confirmed. So 12 B and 24 B ultra-sonic flowmeters were made after additions of several improvements to high temperature problems, and tested in the sodium loop, and it is confirmed that the ultra-sonic flowmeters have superior characteristics as the sodium flowmeters. In the sodium temperature (200 ? 400 deg C) and flow rate (0 ? 6 m/s), linearity and repeatability were within ± 1 %. And effect of upper flow straight pipe length to the ultra-sonic flowmeter output was smaller than in water loop tests. This paper describes mainly the above results of sodium flow tests which showed that ultra-sonic flowmeters are useful as the sodium flowmeter. (author)

1987-01-01

330

Flowmeter and Ground Penetrating Radar: comparison between hydrogeological and geophysical methods  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss a comparison between saturated hydraulic conductivity calculated with Electromagnetic Borehole Flowmeter (EBF) and water content obtained by Ground Penetrating Radar (GPR) Zero Offset Profile (ZOP)

Arato, Alessandro; Villa, Alberto; Godio, Alberto

2012-01-01

331

Investigating the effect of magnetic pipes connected to electromagnetic flowmeters using experimentally validated finite element models  

DEFF Research Database (Denmark)

This paper describes a finite element model for computing the magnetic field distribution in commercial electromagnetic flowmeter designs. The model is validated through an experimental setup, measuring the magnetic flux density in the radial direction at the inner perimeter of the flowmeter wall. The predicted flux densities are in overall good agreement with experimental obtained data. The model is used to evaluate the effect of having magnetic pipes connected to flowmeters of two different designs. Using analytic models, the flowmeter sensitivity is computed both with magnetic and non-magnetic pipes connected.

Christensen, Torben Amby; Willatzen, Morten

2010-01-01

332

Developing a flowmeter for streams with high solids content  

Science.gov (United States)

A type of flowmeter, based on a piping arrangement similar to a Wheatstone bridge, was tested to measure the flow rate of the feed to the Kerr-McGee critical solvent deashing (CSD) unit of the solvent refined coal pilot plant in Wilsonville, Alabama. To simulate the non-Newtonian behavior of the CSD feed stream, mineral oil and a mixture of a polymer, carboxymethyl cellulose, and water were used in the tests. It is shown that there is a direct relationship between the flow rate and the ratio of the pressure drops across the parallel legs of the flowmeter and across a line connecting the center of the parallel legs. A mathematical model, developed previously to predict the dynamics of the flow measuring system, was tested, and the predicted results matched the measured values fairly well.

Johnson, J. K.; Wilson, J. H.

1984-07-01

333

Space Shuttle Hypergol Load Determination Using Nonintrusive Ultrasonic Flowmeters  

Science.gov (United States)

Space Shuttle preflight hypergol oxidizer and fuel loading were monitored using a nonintrusive flow measurement system (NFMS) during preflight operation. A pair of 4-megahertz ultrasonic transducers measured the flow rate using a transit-time flow measurement technique. Using wireless cellular phone technology, flow-rate data was monitored and recorded. Excellent correlation was observed between the flow profiles measured using the proposed nonintrusive ultrasonic flowmeters (UFM's) and those made from conventional intrusive turbine meters (TFM). Based on the preliminary tests, it is concluded that the nonintrusive method of flow measurement has the same or higher accuracy, is simpler, and costs less than the existing TFM. Benefits of UFM's include a highly flexible, cost-effective, reliable, hazard free, and streamlined hypergol operation. Redundant installation of ultrasonic flowmeters was recommended for a few more launches prior to the replacement of the existing TFM.

Werlink, Rudolph; Kelley, Andrew; Margasahayam, Ravi

1996-01-01

334

Flowmetering of natural gas pipelines by tracer gas pulse injection  

International Nuclear Information System (INIS)

We investigate the tracer gas pulse injection method for flowmetering of natural gas pipelines. The principle of the measurement consists of detecting the passage of the pulse at two locations along the pipeline, from which the time of passage is calculated. The measurement accuracy depends on how the pulse form evolves due to turbulent diffusion and convective distortion in the pipe, as well as due to the influence of bends. We discuss these factors to evaluate the applicability of the method to pipelines of kilometer distances. We also perform a three-dimensional numerical analysis to understand the spatial pulse dispersion, and numerical analysis shows that the influence of pipe bends was not significant. Both experimental and theoretical results indicate the existence of axial diffusion coefficients, even in pipelines with bends. These results enable us to predict the evolution of the pulse concentration profile. Finally, we demonstrate acceptable precision for practical flowmetering applications in actual utility pipelines

2010-01-01

335

Flowmetering of natural gas pipelines by tracer gas pulse injection  

Science.gov (United States)

We investigate the tracer gas pulse injection method for flowmetering of natural gas pipelines. The principle of the measurement consists of detecting the passage of the pulse at two locations along the pipeline, from which the time of passage is calculated. The measurement accuracy depends on how the pulse form evolves due to turbulent diffusion and convective distortion in the pipe, as well as due to the influence of bends. We discuss these factors to evaluate the applicability of the method to pipelines of kilometer distances. We also perform a three-dimensional numerical analysis to understand the spatial pulse dispersion, and numerical analysis shows that the influence of pipe bends was not significant. Both experimental and theoretical results indicate the existence of axial diffusion coefficients, even in pipelines with bends. These results enable us to predict the evolution of the pulse concentration profile. Finally, we demonstrate acceptable precision for practical flowmetering applications in actual utility pipelines.

Takeuchi, Tomoaki; Murai, Yuichi

2010-01-01

336

Using the RGD-4 flowmeters in a continuous broaching mode  

Energy Technology Data Exchange (ETDEWEB)

Methods for calibrating flowmeters in oil and injection wells are given. It is demonstrated that as the device moves towards the flow, the reliability of the qualitative and quantitative estimates increases, and the sensitivity to low flow rates increases. A description of a method for connecting the RGD-4 to the standardized panel of the radioactive logging device is given. The results from processing the measurements differ from each other and the data obtained by other method by less than 10-15%.

Avdeev, N.D.; Krugliak, V.G.; Nikitin, A.A.; Parfenov, A.I.

1981-01-01

337

A newly developed borehole flowmeter technology for heterogeneous aquifers  

International Nuclear Information System (INIS)

Extensive borehole flowmeter tests were performed at 37 fully-screened wells on a one-hectare test site to characterize the three-dimensional hydraulic conductivity field of an alluvial aquifer with a ?_l_n_K of 4.7. During the site investigations, several major advancements with respect to borehole flowmeter technology were developed. The milestones included: (1) the development of a field-durable electromagnetic borehole flowmeter with a lower detection limit of 0.1 l/min; (2) the realization of the importance of the pumping rate with respect to the calculated value for the depth-averaged hydraulic conductivity; and (3) an evaluation of alternative methods for calculating the depth-averaged hydraulic conductivity. The predicted three-dimensional hydraulic conductivity field was compared to the results of 10 small-scale (3 to 7 m) tracer tests, information about the depositional history of the aquifer, and the results of three large-scale aquifer tests. The hydraulic conductivity data predict the major features of the tracer breakthrough curves, maps the outline of a former river meander in an aerial photograph, and leads to a geometric mean consistent with the average hydraulic conductivity of the aquifer. (Author) (14 refs., 15 figs., 2 tabs.)

1990-10-01

338

Sub-Doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses  

Science.gov (United States)

We demonstrate sub-Doppler cooling of 40K on the D1 atomic transition. Using a gray-molasses scheme, we efficiently cool a compressed cloud of 6.5 × 108 atoms from ˜4 mK to 20 ?K in 8 ms. After transfer to a quadrupole magnetic trap, we measure a phase space density of ˜10-5. This technique offers a promising route for fast evaporation of fermionic 40K.

Rio Fernandes, D.; Sievers, F.; Kretzschmar, N.; Wu, S.; Salomon, C.; Chevy, F.

2012-12-01

339

Between the Probe and the Pump : An experimental study on cardiac performance analysis based on Echocardiography, tissue and laser Doppler  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Echocardiography is an ultrasound-based bedside, non-invasive and easily available cardiac diagnostic technique visualising the heart’s morphology and function. Quantification of cardiac wall motion can be measured with the tissue Doppler Imaging (TDI) modality which provides in humans a high diagnostic capacity to differentiate healthy from diseased myocardium with reduced function. Heart failure, as a consequence of, for example, myocardial or ischaemic heart disease, demands both bedside...

Hu?bbert, Laila

2010-01-01

340

Investigation and Comparison of In-Flight Particle Velocity During the Plasma-Spray Process as Measured by Laser Doppler Anemometry and DPV-2000  

Science.gov (United States)

Plasma spraying has become one of the most important thermal-spray technologies due to low operating costs, high deposition rates, and a high efficiency. It is especially suitable for producing coatings used to improve thermal, corrosion, and wear protection. The quality of coatings produced by thermal-spray processes are determined by particle characteristics, such as in-flight velocity, which can be investigated using various diagnostic systems. Velocity is a particularly relevant parameter for small particles, but it is difficult to measure. Hence, different velocity diagnostics must be validated for small injected particles. We compared the laser Doppler anemometry (LDA) system with the DPV-2000 system and measured the particle velocities of a F4 plasma torch. The results agreed well when the limited detectability of small particles by LDA was taken into account.

Mauer, G.; Vaßen, R.; Zimmermann, S.; Biermordt, T.; Heinrich, M.; Marques, J.-L.; Landes, K.; Schein, J.

2013-08-01

 
 
 
 
341

Laser Doppler sensor employing a single fan-shaped interference fringe system for distance and shape measurement of laterally moving objects  

International Nuclear Information System (INIS)

For monitoring the position and shape of fast moving and, especially, rotating objects such as turbo machine rotors, contactless and compact sensors with a high measurement rate as well as high precision are required. We present for the first time, to the best of our knowledge, a novel laser Doppler sensor employing a single fan-shaped interference fringe system, which allows measuring for the position and shape of fast moving solid bodies with known tangential velocity. It is shown theoretically as well as experimentally that this sensor offers concurrently high position resolution and high temporal resolution in contrast to conventional measurement techniques, since its measurement uncertainty is, in principle, independent of the object velocity. Moreover, it can be built very compact, because it features low complexity. To prove its operational capability and its potential for practical applications, radial and axial shape measurements of rotating bodies are demonstrated in comparison with triangulation. An average position resolution of about 2 ?m could be achieved

2009-01-01

342

Frequency stabilization of Nd:YAG lasers to {sup 133}Cs{sub 2} sub-Doppler lines near 1064 nm  

Energy Technology Data Exchange (ETDEWEB)

Sub-Doppler lines of Cs{sub 2} were investigated with a Nd:YAG laser. Modulation transfer spectroscopy and FM spectroscopy were applied to yield error signals that were used for absolute stabilization of the laser frequency. The frequency stability was characterized with an I{sub 2}-locked dual-wavelength Nd:YAG frequency reference. The root Allan variance of the beat frequency reached a minimum of 1.3{times}10{sup {minus}11} (beat frequency fluctuations of 3.65 kHz) for a measurement time of 20 s. Absolute frequencies of several Cs{sub 2} lines were determined with an accuracy of {approximately}1 MHz. Further improvement in sensitivity was demonstrated by insertion of the absorption cell into a Fabry{endash}Perot cavity. While the laser was locked to the cavity, the cavity length was modulated and the transmitted probe beam was detected at the third harmonic of the modulation frequency. {copyright} {ital 1996 Optical Society of America.}

Inbar, E.; Mahal, V.; Arie, A. [Department of Electrical Engineering---Physical Electronics, Faculty of Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv, (Israel) 69978

1996-07-01

343

Frequency Swept Diode-pumped Single Frequency TM,Ho:YLiF Laser for spaceborne Doppler Lidar  

Science.gov (United States)

Optical heterodyne experiments involving the photomixing of two single frequency, deode-pumped thulium holmium yttrium lithium flouride lasers are described. Operated in external frquency stabilization loops, the lasers exhibit 1MHz short term stability, and are photomixed and offset-locked at 140 MHz. Summation of sine wave modulation onto the PZT control voltage on one laser results in frequency swept operation over a continuous tuning range of 160 MHz.

McGuckin, B. T.; Menzies, R. T.; Esproles, C.

1993-01-01

344

Design and development of drag-disc flowmeter for measurement of transient two-phase flow  

International Nuclear Information System (INIS)

Experiments have been carried out to test the suitability of drag-disc flowmeter for measuring two-phase flow. Calibration tests carried out under single-phase and two-phase flow conditions have confirmed the suitability of the drag-disc flowmeter. The experimental work and the results obtained are presented and discussed in the paper. (author). 3 refs., 6 figs

1990-01-01

345

Basic doppler echocardiography  

Energy Technology Data Exchange (ETDEWEB)

This book contains 12 chapters. Some of the chapter titles are: An Introduction to Doppler; Pulsed and Continuous Wabe Doppler; The Doppler Examination; Doppler Evaluation of Valvular Regurgitation; Doppler Evaluation of Valvular Stenosis; and Pulsed Doppler Analysis of Human Fetal Blood Flow.

Kisslo, J.; Adams, D.; Mark, D.B.

1986-01-01

346

DOPPLER-FREE TWO-PHOTON LASER SPECTROSCOPY OF RYDBERG STATES IN ALKALINE-EARTH ELEMENTS WITH THERMIONIC DETECTION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Doppler-free two-photon spectroscopy was applied to investigate level energies, isotope shifts and hyperfine structures of msns and msnd Rydberg series of alkaline earth elements Mg (m=3), Ca (m=4 ), Sr (m=5) and Ba (m=6) between principal quantum numbers n=3 and 150. As a result configuration interactions, singlet-triplet mixing and hyperfine-induced effects were detected. The use of a thermionic ring diode allowed for high resolution measurements up to principal quantum numbers n ~ 160.

Beigang, R.; Timmermann, A.

1983-01-01

347

Doppler-free laser spectroscopy measurements on a Ne discharge for determination of 22Ne-20Ne isotope shifts  

International Nuclear Information System (INIS)

The authors have used Doppler-free polarization spectroscopy, intermodulated fluorescence and intermodulated optogalvanic spectroscopy for measuring isotope shifts in 6 Ne lines connecting the 2p53s and 2p53p configurations. The measurements were performed on two different hollow cathodes. For the 5852, 5882, 5945, 5976, 6143 and 6164 A lines the 22Ne-20Ne isotope shift was found to be 2300(15), 1740(2), 1717(3), 1728(5), 1669(4) and 1663(5) MHz, respectively. These results are in fair agreement with previous optical spectroscopy data. (Auth.)

1983-01-01

348

Doppler and the Doppler Effect.  

Science.gov (United States)

A summary is given of Doppler's life and career. He was born 180 years ago on 29 Nov 1803 in Salzburg, Austria. He died on 17 Mar 1853 in Venice. The effect bearing his name was first announced in a presentation before the Royal Bohemian Society of the Sc...

K. Toman

1984-01-01

349

Evaluation of several ultrasonic flowmeter transducers in cryogenic environment  

Science.gov (United States)

Eighteen piezoelectric ultrasonic flowmeter transducers were laboratory tested to determine their suitability and long range reliability for use by the National Transonic Facility (NTF) to measure the flow rate of 450 Kg/sec of liquid nitrogen (LN2). Tests included thermally cycling each transducer 50 to 150 times over a temperature range of 295 K (ambient) to 77 K (LN2). The transducers were submerged in liquid nitrogen for 1 to 4 hours and the signal strength and quality noted. Results disclose that the current state-of-the-art ultrasonic flow transducers are very reliable and will meet the stringent requirements of the NTF.

Moughon, W. C.

1981-01-01

350

A pulsed phase measurement ultrasonic flowmeter for medical gases.  

Science.gov (United States)

Pneumotachometers are used to measure instantaneous flowrate in the respiratory gas streams. The presently available devices suffer from lack of linearity, slow response times, and gas density sensitivity. A new design of an ultrasonic gas flowmeter is presented in this paper: We investigate the acoustic characteristics of ring and piston shaped transducers, and describe a sampling method to avoid the error due to reflection. A microcomputer is used to overcome the 360 degrees detection ambiguity problem associated with phase detection technique. This design has been tested in clinical settings and has been shown to give linear response, independent of gas density, and to have a wide dynamic range. PMID:6240213

Kou, A H; Peickert, W R; Polenske, E E; Busby, M G

1984-01-01

351

Evaluation of human hemispheric blood flow based on noninvasive carotid blood flow measurements using the range-gated Doppler technique  

International Nuclear Information System (INIS)

Common carotid blood flow (CCBF) was measured in 11 anesthetised patients without extracranial arterial disease (nine acute subarachnoid haemorrhages and two cases of head injury). The range-gated Doppler flowmeter with an adjustable range-gated time system and a double transducer probe was used to determine diameter, blood velocity, and blood flow of the common carotid artery. Values were, respectively, 5.9 +/- 1.1 mm, 13.8 +/- 6.1 cm . sec-1 and 387 +/- 183 cm3. min-1. Mean cerebral blood flow (rCBF) measurements were simultaneously made by 133Xe intra-arterial method, with a value of 22.28 +/- 5.96 ml . min-1 . 100 g. High correlation coefficient was found between CCBF and mean rCBF (r . 0.73, p less than 0.001). The range-gated Doppler flowmeter thus provides a non invasive and easily duplicated method for monitoring cerebral blood flow in anesthetized patients

1982-01-01

352

Design and development of primary orifice plate flowmeter  

International Nuclear Information System (INIS)

Accurate and stable gas flows are very important in different applications like, the performance study of vacuum pumps, gauge calibration, leak detection and advance research in low pressure physics. Primary Orifice Plate Flowmeter (OPF) has been designed and developed indigenously. This flowmeter consists of two orifice plates. Orifice-1 (O1) acts as a flow restriction, while orifice-2 (O2) enables continuous pumping mode. By varying upstream pressure P1, a change in downstream pressure P2 is recorded, and the flow-rate is calculated from the conductance 'C' of the orifice O1 and pressure difference by the relation Q = C(P1 ? P2). Main feature of this primary OPF is that it is very simple and compact. A stable and reproducible flow-rate has been achieved in the range of 10?5 to 10?6 mbar.l/s. A variation in Q has been observed with a change in temperature of orifice and orifice diameter.

2013-06-10

353

Self-mixing laser Doppler vibrometry with high optical sensitivity application to real-time sound reproduction  

CERN Document Server

Nanometre vibration measurement of an audio speaker and a highly sensitive sound reproduction experiment have been successfully demonstrated by a self-aligned optical feedback vibrometry technique using the self-mixing modulation effect in a laser-diode-pumped microchip solid-state laser. By applying nanometre vibrations to the speaker, which produced nearly inaudible music below 20 dB (200 mu Pa) sound pressure level, we could reproduce clear sound in real time by the use of a simple frequency modulated wave demodulation circuit with a -120 dB light-intensity feedback ratio.

Abe, K; Ko, J Y

2003-01-01

354

A study of doppler waveform using pulsatile flow model  

Energy Technology Data Exchange (ETDEWEB)

Through the construction of a pulsatile flow model using an artificial heart pump and stenosis to demonstrate triphasic Doppler waveform, which simulates in vivo conditions, and to evaluate the relationship between Doppler waveform and vascular compliance. The flow model was constructed using a flowmeter, rubber tube, glass tube with stenosis, and artificial heart pump. Doppler study was carried out at the prestenotic, poststenotic, and distal segments;compliance was changed by changing the length of the rubber tube. With increasing proximal compliance, Doppler waveforms show decreasing peak velocity of the first phase and slightly delayed acceleration time, but the waveform itself did not change significantly. Distal compliance influenced the second phase, and was important for the formation of pulsus tardus and parvus, which without poststenotic vascular compliance, did not develop. The peak velocity of the first phase was inversely proportional to proximal compliance, and those of the second and third phases were directly proportional to distal compliance. After constructing this pulsatile flow model, we were able to explain the relationship between vascular compliance and Doppler waveform, and also better understand the formation of pulsus tardus and parvus.

Chung, Hye Won [Seoul City Boramae Hospital, Seoul (Korea, Republic of); Chung, Myung Jin; Park, Jae Hyung; Chung, Jin Wook; Lee, Dong Hyuk; Min, Byoung Goo [Seoul National Univ. College of Medicine, Seoul (Korea, Republic of)

1997-08-01

355

Laser Doppler interferometer based on a solid Fabry–Perot etalon for measurement of surface velocity in shock experiments  

International Nuclear Information System (INIS)

This study presents an original optical system designed for measuring the free surface velocity for shock wave diagnostics. The system is based on a solid Fabry–Perot etalon interferometer coupled to a tunable, single frequency laser. The setup assembled for this purpose can measure velocities up to 200 m s?1 and has a resolution time of about 1 ns. This system was validated in shock experiments performed on thin aluminum samples. The shock waves were generated by a pulsed laser on a water confinement configuration and the surface velocity was measured on the opposite side of the sample. The signals obtained are in good agreement with numerical simulation and results found in the literature. This system presents an interesting alternative to the velocity interferometer system for any reflectors (VISAR) commonly used in shock experiments

2009-01-01

356

Contribution of laser Doppler velocimetry to the physical description of shock wave/turbulent boundary layer interactions with incidence on turbulence modelling  

Science.gov (United States)

With the advent of Laser Doppler Velocimetry (LDV) in the 1970's, it became possible to investigate high speed complex flows containing shock waves, separated regions, and strong turbulent fluctuations. This powerful tool has allowed an unprecedented physical description of the flow fields resulting from shock wave/boundary layer interaction, both in two- and three-dimensional flows. It is remarkable that the development of LDV accompanied the progress in CFD, thus permitting an in depth validation of the theoretical models. The Lecture focusses on the use of LDV to investigate typical transonic and supersonic interactions occurring, firstly in nominally 2D configurations, then in a 3D channel flow. The data thus obtained are used to validate a detailed description of the flow field and to validate several equilibrium and non-equilibrium turbulence models. In 2D flows, the calculations were executed by using an economical boundary layer type approach, for the 3D case the models were implemented in a Navier-Stokes code.

Delery, J. M.

1993-08-01

357

Comparative potency of formulations of mometasone furoate in terms of inhibition of ?PIRHR? in the forearm skin of normal human subjects measured with laser doppler velocimetry  

Directory of Open Access Journals (Sweden)

Full Text Available BACKGROUND AND AIMS: Topical glucocorticoid formulations are widely used for effective treatment and control of a variety of dermatoses. Mometasone furoate is a newer corticoid that has high potency but low systemic toxicity. Pharmaceutical factors are known to significantly influence potency and systemic absorption of topically applied glucocorticoids. We studied the potency of "Elocon", a topical formulation of mometasone furoate, compared with two other branded formulations of the same corticoid. METHODS: Corticoid potency was measured by employing a pharmacodynamic parameter of an inhibitory effect of the corticoid on post-ischemic-reactive-hyperemic-response (PIRHR in human forearm skin under occlusive dressing. The PIRHR was expressed in terms of % increase in the skin blood flow (SBF as measured with laser doppler velocimetry (LDV. RESULTS : All three active branded formulations of mometasone furoate produced significant inhibition of PIRHR. The AUC(0-2min of PIRHR was ( Mean ± SEM , Control = 213.52 ± 11.80, Placebo = 209.77 ± 19.31, Formulation A = 119.83 ± 13.71, Formulation C = 53.67 ± 4.85 and Formulation D = 111.46 ± 22.87. Formulation "C" exhibited significantly higher topical anti-inflammatory potency than formulations "A" or "D". CONCLUSIONS: Thus, branded formulations of the same glucocorticoid, mometasone furoate significantly differed in their topical anti-inflammatory potency. "Elocon" was significantly more potent than the two other branded formulations studied.

Kulhalli Prabhakar

2005-01-01

358

Spectral components of laser Doppler flowmetry signals recorded in healthy and type 1 diabetic subjects at rest and during a local and progressive cutaneous pressure application: scalogram analyses  

Science.gov (United States)

A significant transient increase in laser Doppler flowmetry (LDF) signals is observed in response to a local and progressive cutaneous pressure application in healthy subjects. This reflex may be impaired in diabetic patients. The work presents a signal processing providing the clarification of this phenomenon. Scalogram analyses of LDF signals recorded at rest and during a local and progressive cutaneous pressure application are performed on healthy and type 1 diabetic subjects. Three frequency bands, corresponding to myogenic, neurogenic and endothelial related metabolic activities, are studied. The results show that, at rest, the scalogram energy of each frequency band is significantly lower for diabetic patients than for healthy subjects, but the scalogram relative energies do not show any statistical difference between the two groups. Moreover, the neurogenic and endothelial related metabolic activities are significantly higher during the progressive pressure than at rest, in healthy and diabetic subjects. However, the relative contribution of the endothelial related metabolic activity is significantly higher during the progressive pressure than at rest, in the interval 200-400 s following the beginning of the pressure application, but only for healthy subjects. These results may improve knowledge on cutaneous microvascular responses to injuries or local pressures initiating diabetic complications.

Humeau, Anne; Koïtka, Audrey; Abraham, Pierre; Saumet, Jean-Louis; L'Huillier, Jean-Pierre

2004-09-01

359

Time-frequency analysis of laser Doppler flowmetry signals recorded in response to a progressive pressure applied locally on anaesthetized healthy rats  

International Nuclear Information System (INIS)

The laser Doppler flowmetry technique has recently been used to report a significant transient increase of the cutaneous blood flow signal, in response to a local non-noxious pressure applied progressively on the skin of both healthy humans and rats. This phenomenon is not entirely understood yet. In the present work, a time-frequency analysis is applied to signals recorded on anaesthetized healthy rats, at rest and during a cutaneous pressure-induced vasodilation (PIV). The comparison, at rest and during PIV, of the scalogram relative energies and scalogram relative amplitudes in five bands, corresponding to five characteristic frequencies, shows an increased contribution for the endothelial related metabolic activity in PIV signals, till 400 s after the beginning of the progressive pressure application. The other subsystems (heart, respiration, myogenic and neurogenic activities) contribute relatively less during PIV than at rest. The differences are statistically significant for all the relative activities in the interval 0-200 s following the beginning of the pressure. These results and others obtained on patients, such as diabetics, could increase the understanding of some cutaneous pathologies involved in various neurological diseases and in the pathophysiology of decubitus ulcers

2004-03-07

360

Study of time reversibility/irreversibility of cardiovascular data: theoretical results and application to laser Doppler flowmetry and heart rate variability signals  

Science.gov (United States)

Time irreversibility can be qualitatively defined as the degree of a signal for temporal asymmetry. Recently, a time irreversibility characterization method based on entropies of positive and negative increments has been proposed for experimental signals and applied to heart rate variability (HRV) data (central cardiovascular system (CVS)). The results led to interesting information as a time asymmetry index was found different for young subjects and elderly people or heart disease patients. Nevertheless, similar analyses have not yet been conducted on laser Doppler flowmetry (LDF) signals (peripheral CVS). We first propose to further investigate the above-mentioned characterization method. Then, LDF signals, LDF signals reduced to samples acquired during ECG R peaks (LDF_RECG signals) and HRV recorded simultaneously in healthy subjects are processed. Entropies of positive and negative increments for LDF signals show a nonmonotonic pattern: oscillations—more or less pronounced, depending on subjects—are found with a period matching the one of cardiac activity. However, such oscillations are not found with LDF_RECG nor with HRV. Moreover, the asymmetry index for LDF is markedly different from the ones of LDF_RECG and HRV. The cardiac activity may therefore play a dominant role in the time irreversibility properties of LDF signals.

Humeau-Heurtier, Anne; Mahé, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Abraham, Pierre

2012-07-01

 
 
 
 
361

MICROCIRCULATION UNDER AN ELASTIC BANDAGE DURING REST AND EXERCISE - PRELIMINARY EXPERIENCE WITH THE LASER-DOPPLER SPECTROPHOTOMETRY SYSTEM O2C  

Directory of Open Access Journals (Sweden)

Full Text Available There is an abundace of studies on the influence of rest and exercise as well as external compression on cutaneous, subcutaneous and muscle tissue blood flow using different measurement techniques. As a novel approach, we simultaneously examined the influence of a custom- made elastic thigh bandage on cutaneous and subcutaneous venous blood oxygenation (SO2, postcapillary venous filling pressures (rHb and blood flow (flow using the non-invasive laser- Doppler spectrophotometry system "Oxygen-to-see(O2C". Parameters were obtained in 20 healthy volunteers in 2 mm and 8 mm tissue depth during rest, 5 and 10 minutes of moderate bicycle exercise following a 10-minute recovery period. Without the bandage, results matched the known physiological changes indicating higher blood backflow from superficial and deep veins. Underneath the elastic bandage, we observed lower post-capillary filling pressures during exercise. However, after the bandage was removed in the post-exercise period, all obtained parameters of microcirculation remained increased, indicating a higher amount of local venous blood volume in this area. Our observations might be the result of external compression, thermoregulatory and exercise-dependent vascular mechanisms. With the O2C device, a promising new non- invasive technique of measuring local microcirculation in soft tissue exists. This study gives new insights in the field of non-invasive diagnostics with special regard to the influence of elastic bandages on local microcirculation

Hans-Martin Sommer

2013-09-01

362

Local drag reduction due to injection of polymer solutions into turbulent flow in a pipe; part II: laser-Doppler measurements of turbulent structure  

Energy Technology Data Exchange (ETDEWEB)

Aqueous solutions of polyethyleneoxide (Polyox WSR-301) were injected into a pipe flow through either a small tube at the center line or an annular slot in the wall. The solution contained polymer at an injection concentration of 1,000 wppm. Injection into water flow with a Reynolds number Re = 3.5 X 10/sup 4/ was at a rate which gave a mean polymer concentration of 5.0 wppm in the water flow. A laser-Doppler anemometer (LDA) was used to measure the streamwise turbulent velocity at various radial positions and at several stations downstream from the injection point. Results were obtained for mean velocity and intensity profiles; autocorrelations; and one-dimensional energy spectra. The mean bursting period was determined using the ''short-sampling-time'' autocorrelation method. Changes in all these quantities due to polymer injection were found to depend on the amount of local drag reduction at that particular downstream station but were independent of the local polymer concentration at the measuring point.

McComb, W.D.; Rabie, L.H.

1982-07-01

363

Dynamic characteristics of the cutaneous vasodilator response to a local external pressure application detected by the laser Doppler flowmetry technique on anesthetized rats  

Science.gov (United States)

The laser Doppler flowmetry technique has recently been used to report a significant transient increase of the cutaneous blood flow signal when a local non-noxious pressure is applied progressively on the skin (11.1 Pa/s). The present work analyses the dynamic characteristics of this vasodilatory reflex response on anaesthetised rats. A de-noising algorithm using wavelets is proposed to obtain accurate values of these dynamic characteristics. The blood flow peak and the time to reach this peak are computed on the de-noised recordings. The results show that the mean time to reach the peak of perfusion is 85.3 s (time t = 0 at the beginning of the pressure application). The mean peak value is 188.3 arbitrary units (a.u.), whereas the mean value of the perfusion before the pressure application is 113.4 a.u. The mean minimum value obtained at the end of the experiment is 60.7 a.u. This latter value is, on the average, reached 841.3 s after the beginning of the pressure application. The comparison of the dynamic characteristics, computed with the de-noising algorithm on signals obtained in other situations, will give a better understanding on some cutaneous lesions such as those present on diabetic people.

Humeau, Anne; Koitka, Audrey; Saumet, Jean-Louis; L'Huillier, Jean-Pierre

2003-10-01

364

Local cooling reduces skin ischemia under surface pressure in rats: an assessment by wavelet analysis of laser Doppler blood flow oscillations.  

Science.gov (United States)

The objectives of this study were to investigate the effects of local cooling on skin blood flow response to prolonged surface pressure and to identify associated physiological controls mediating these responses using the wavelet analysis of blood flow oscillations in rats. Twelve Sprague-Dawley rats were randomly assigned to three protocols, including pressure with local cooling (?t = -10 °C), pressure with local heating (?t = 10 °C) and pressure without temperature changes. Pressure of 700 mmHg was applied to the right trochanter area of rats for 3 h. Skin blood flow was measured using laser Doppler flowmetry. The 3 h loading period was divided into non-overlapping 30 min epochs for the analysis of the changes of skin blood flow oscillations using wavelet spectral analysis. The wavelet amplitudes and powers of three frequencies (metabolic, neurogenic and myogenic) of skin blood flow oscillations were calculated. The results showed that after an initial loading period of 30 min, skin blood flow continually decreased under the conditions of pressure with heating and of pressure without temperature changes, but maintained stable under the condition of pressure with cooling. Wavelet analysis revealed that stable skin blood flow under pressure with cooling was attributed to changes in the metabolic and myogenic frequencies. This study demonstrates that local cooling may be useful for reducing ischemia of weight-bearing soft tissues that prevents pressure ulcers. PMID:23010955

Jan, Yih-Kuen; Lee, Bernard; Liao, Fuyuan; Foreman, Robert D

2012-10-01

365

Time-frequency analysis of laser Doppler flowmetry signals recorded in response to a progressive pressure applied locally on anaesthetized healthy rats  

Energy Technology Data Exchange (ETDEWEB)

The laser Doppler flowmetry technique has recently been used to report a significant transient increase of the cutaneous blood flow signal, in response to a local non-noxious pressure applied progressively on the skin of both healthy humans and rats. This phenomenon is not entirely understood yet. In the present work, a time-frequency analysis is applied to signals recorded on anaesthetized healthy rats, at rest and during a cutaneous pressure-induced vasodilation (PIV). The comparison, at rest and during PIV, of the scalogram relative energies and scalogram relative amplitudes in five bands, corresponding to five characteristic frequencies, shows an increased contribution for the endothelial related metabolic activity in PIV signals, till 400 s after the beginning of the progressive pressure application. The other subsystems (heart, respiration, myogenic and neurogenic activities) contribute relatively less during PIV than at rest. The differences are statistically significant for all the relative activities in the interval 0-200 s following the beginning of the pressure. These results and others obtained on patients, such as diabetics, could increase the understanding of some cutaneous pathologies involved in various neurological diseases and in the pathophysiology of decubitus ulcers.

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

2004-03-07

366

Study of time reversibility/irreversibility of cardiovascular data: theoretical results and application to laser Doppler flowmetry and heart rate variability signals  

International Nuclear Information System (INIS)

Time irreversibility can be qualitatively defined as the degree of a signal for temporal asymmetry. Recently, a time irreversibility characterization method based on entropies of positive and negative increments has been proposed for experimental signals and applied to heart rate variability (HRV) data (central cardiovascular system (CVS)). The results led to interesting information as a time asymmetry index was found different for young subjects and elderly people or heart disease patients. Nevertheless, similar analyses have not yet been conducted on laser Doppler flowmetry (LDF) signals (peripheral CVS). We first propose to further investigate the above-mentioned characterization method. Then, LDF signals, LDF signals reduced to samples acquired during ECG R peaks (LDFRECG signals) and HRV recorded simultaneously in healthy subjects are processed. Entropies of positive and negative increments for LDF signals show a nonmonotonic pattern: oscillations—more or less pronounced, depending on subjects—are found with a period matching the one of cardiac activity. However, such oscillations are not found with LDFRECG nor with HRV. Moreover, the asymmetry index for LDF is markedly different from the ones of LDFRECG and HRV. The cardiac activity may therefore play a dominant role in the time irreversibility properties of LDF signals. (paper)

2012-07-07

367

A real-time ultrasound time-domain correlation blood flowmeter. I. Theory and design.  

Science.gov (United States)

A real-time ultrasound time-domain correlation (UTDC) blood flowmeter has been developed. Real-time performance has been achieved through the implementation of a custom-designed high-speed residue-number system (RNS) hardware correlator. The flowmeter is interfaced to a commercial ultrasound imager and can produce one-dimensional velocity versus range graphs at a rate of three per second. It has been validated in a blood flow phantom under a variety of conditions along with in vivo measurements in the human carotid artery. The theory of the time-domain correlation technique, design and implementation of flowmeter hardware, and the important correlation parameters which affect the performance of the flowmeter are described. PMID:18263245

Hein, I A; Chen, J T; Jenkins, W K; O'Brien, W R

1993-01-01

368

E.M.I Effects of Cathodic Protection on Electromagnetic Flowmeters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Electromagnetic flowmeters are used to measure the speed of water flow in water distribution systems. Corrosion problem in metal pipelines can be solved by cathodic protection methods. This paper presents a research on corruptive effects of the cathodic protection system on electromagnetic flowmeter depending on its measuring principle. Experimental measurements are realized on the water distribution pipelines of the Izmir Municipality, Department of Water and Drainage Administration (IZSU) i...

Serdar Gundogdu; Ozge Sahin

2007-01-01

369

Effects of pulsating flow on an ultrasonic gas flowmeter  

Energy Technology Data Exchange (ETDEWEB)

A series of tests was carried out to assess the effects of pulsating flow on a small-dimension ultrasonic gas flowmeter. Three different parameters were investigated: pulsation amplitude; pulsation frequency and mean flow velocity. The measurements were carried out in air at mean flow rates from 1.2 to 9.6 m s[sup -1], using four different pulsation frequencies (2, 5, 10 and 20 Hz) with pulsation amplitudes from 0 to [approx] 70% r.m.s. The measurements reveal three major phenomena affecting performance. (1) Sampling phenomena, i.e. aliasing: (2) Errors due to changes of the flow profile caused by an imaginary high Reynolds number (3) Non-linearities when averaging very high or low flow velocities, respectively. For the meter tested, this results in large negative errors due to non-linearities on the extremes of the error curve of the meter. (Author)

Haakansson, E.; Delsing, J. (Lund Inst. of Tech. (Sweden). Div. of Heat and Power Engineering)

1994-04-01

370

New transit time flowmeter system for PWR coolant flow measurement  

International Nuclear Information System (INIS)

The power generating capability of pressurized water reactors is strictly dependent on the coolant flow rate through the reactor core. Conventional methods of coolant flow-rate measurement involve uncertainties which have to be compensated for by conservatism in the rated output of the core. It has long been realized that for primary-coolant flow-rate measurement a direct method would be desirable for the fine control of nuclear reactors in order to obtain maximum performance. Transit time flow measurement based on the calculation of the cross-correlation function has been used successfully for accurate PWR flow control in industry. In this method the _1_6N activity fluctuations of the flowing water in the primary-coolant loops are utilized for determining the mean transit time needed to cover the distance between two gamma-radiation detectors. The first part of the paper deals with theoretical developments in this field and with the experimental results obtained at the Hungarian WWR-SM research reactor. A new, unshielded and specially formed _1_6N gamma-radiation detector is described. The design concepts of the preamplifiers and signal conditioners are discussed. Also, a Z-80 microprocessor-based multi-channel flowmeter is described which has been developed for the industrial application of the above method. The hardware and software assembly of this instrument is discussed in detail. Finally, the CORR-FLOW M6 flowmeter system to be put in operation in the first Hungarian PWR in Paks is briefly described. The system is able to measure simultaneously the volumetric and mass flow rates of every coolant loop in a PWR. The measured and stored values can be visualized on a video monitor or a digital display. (author)

1982-10-11

371

The performance of electromagnetic flowmeters in a liquid metal two-phase flow  

International Nuclear Information System (INIS)

In order to investigate the characteristics of an electromagnetic flowmeter in a liquid metal two-phase flow, AC electromagnetic flowmeters were designed and manufactured. Two-phase flow experiments, encompassing bubbly to slug flow regimes, were realized with a water-air mixture and a liquid sodium-nitrogen mixture, respectively. The relation ?UTP=?USP/(1-?), between the flow induced electromotive force (e.m.f.) of a single-phase flow and that of a two-phase flow, was verified by the measured e.m.f.s. and the void fraction ? for a bubbly flow regime. Whereas there is no difference in the shape of the flow induced e.m.f. between single-phase and bubbly flow, the signal amplitude of the bubbly flow is greater than that of the single-phase flow under the same water or liquid sodium flow rate, since the real liquid velocity is higher than that of the single-phase flow. In the case of a slug flow, the phase and the amplitude of the flowmeter output changed drastically when a slug bubble passed through the flowmeter. Therefore, the electromagnetic flowmeter shows good potential as a useful device for identifying the flow regimes. The void fraction in a bubbly flow can be measured using two electromagnetic flowmeters. (author)

2003-10-01

372

Comparison of UNL laser imaging and sizing system and a phase Doppler system for analyzing sprays from a NASA nozzle  

Science.gov (United States)

Research was conducted on characteristics of aerosol sprays using a P/DPA and a laser imaging/video processing system on a NASA MOD-1 air assist nozzle being evaluated for use in aircraft icing research. Benchmark tests were performed on monodispersed particles and on the NASA MOD-1 nozzle under identical lab operating conditions. The laser imaging/video processing system and the P/DPA showed agreement on a calibration tests in monodispersed aerosol sprays of + or - 2.6 micron with a standard deviation of + or - 2.6 micron. Benchmark tests were performed on the NASA MOD-1 nozzle on the centerline and radially at 0.5 inch increments to the outer edge of the spray plume at a distance 2 ft downstream from the exit nozzle. Comparative results at two operation conditions of the nozzle are presented for the two instruments. For the 1st case studied, the deviation in arithmetic mean diameters determined by the two instruments was in a range of 0.1 to 2.8 micron, and the deviation in Sauter mean diameters varied from 0 to 2.2 micron. Severe operating conditions in the 2nd case resulted in the arithmetic mean diameter deviating from 1.4 to 7.1 micron and the deviation in the Sauter mean diameters ranging from 0.4 to 6.7 micron.

Alexander, Dennis R.

1990-01-01

373

Effects of prolonged surface pressure on the skin blood flowmotions in anaesthetized rats-an assessment by spectral analysis of laser Doppler flowmetry signals  

International Nuclear Information System (INIS)

The objective of this study is to assess the effect of prolonged surface compression on the skin blood flowmotion in rats using spectral analysis based on wavelets transform of the periodic oscillations of the cutaneous laser Doppler flowmetry (LDF) signal. An external pressure of 13.3 kPa (100 mmHg) was applied to the trochanter area and the distal lateral tibia of Sprague-Dawley rats via two specifically designed pneumatic indentors. The loading duration was 6 hours/day for 4 consecutive days. Five frequency intervals were identified (0.01-0.04 Hz, 0.04-0.15 Hz, 0.15-0.4 Hz, 0.4-2 Hz and 2-5 Hz) corresponding to endothelial related metabolic, neurogenic, myogenic, respiratory and cardiac origins. The absolute amplitude of oscillations of each particular frequency interval and the normalized amplitude were calculated for quantitative assessments. The results showed that (1) tissue compression following the above schedule induced significant decrease in the normalized amplitude in the frequency interval of 0.01-0.04 Hz both in the trochanter area (p < 0.001) and tibialis area (p = 0.023) (2) prolonged compression induced significant increase in the absolute amplitude (p = 0.004 for the trochanter area and p = 0.017 for the tibialis area) but significant decrease in the normalized amplitude (p = 0.023 for the trochanter area and p = 0.026 for the tibialis area) in the frequency interval of 0.15-0.4 Hz, and (3) at the tibialis area, the flowmotion amplitude (frequency interval 0.15-0.4 Hz) measured prior to the daily tissue compression schedule was found to be significantly higher on day 4 than the measurements obtained on day 1. However, this finding was not observed at the trochanter area. Our results suggested that prolonged compression might induce endothelial damage and affect the endothelial related metabolic activities

2006-05-21

374

Effects of prolonged surface pressure on the skin blood flowmotions in anaesthetized rats-an assessment by spectral analysis of laser Doppler flowmetry signals  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to assess the effect of prolonged surface compression on the skin blood flowmotion in rats using spectral analysis based on wavelets transform of the periodic oscillations of the cutaneous laser Doppler flowmetry (LDF) signal. An external pressure of 13.3 kPa (100 mmHg) was applied to the trochanter area and the distal lateral tibia of Sprague-Dawley rats via two specifically designed pneumatic indentors. The loading duration was 6 hours/day for 4 consecutive days. Five frequency intervals were identified (0.01-0.04 Hz, 0.04-0.15 Hz, 0.15-0.4 Hz, 0.4-2 Hz and 2-5 Hz) corresponding to endothelial related metabolic, neurogenic, myogenic, respiratory and cardiac origins. The absolute amplitude of oscillations of each particular frequency interval and the normalized amplitude were calculated for quantitative assessments. The results showed that (1) tissue compression following the above schedule induced significant decrease in the normalized amplitude in the frequency interval of 0.01-0.04 Hz both in the trochanter area (p < 0.001) and tibialis area (p = 0.023) (2) prolonged compression induced significant increase in the absolute amplitude (p = 0.004 for the trochanter area and p = 0.017 for the tibialis area) but significant decrease in the normalized amplitude (p = 0.023 for the trochanter area and p = 0.026 for the tibialis area) in the frequency interval of 0.15-0.4 Hz, and (3) at the tibialis area, the flowmotion amplitude (frequency interval 0.15-0.4 Hz) measured prior to the daily tissue compression schedule was found to be significantly higher on day 4 than the measurements obtained on day 1. However, this finding was not observed at the trochanter area. Our results suggested that prolonged compression might induce endothelial damage and affect the endothelial related metabolic activities.

Li Zengyong [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Tam, Eric W C [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Kwan, Maggie P C [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Mak, Arthur F T [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Lo, Samuel C L [Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Leung, Mason C P [Department of Rehabilitation Sciences, Hong Kong Polytechnic University, Kowloon, Hong Kong (China)

2006-05-21

375

Microcirculation in the upper trapezius muscle during sustained shoulder load in healthy women--an endurance study using percutaneous laser-Doppler flowmetry and surface electromyography.  

Science.gov (United States)

Microcirculation in the upper portion of the trapezius muscle was measured percutaneously in a group of 16 healthy women of different ages by continuous laser-Doppler flowmetry (LDF) in relation to electromyography (EMG) during an endurance test. During the measurements the subject kept her arms straight and elevated at 45 degrees in the scapular plane and held a 1-kg load in each hand as long as possible. This was followed by rest with the arms hanging and carrying no load. The 10-min recording period comprised 1-min initial rest followed by the endurance test and then recovery. Signal processing was done by computer on line. The LDF and root-mean-square (rms) EMG signals were normalized. Spectrum analyses of EMG mean power frequency (MPF) were performed. The amount of load produced was on average 2,267 (SD 939) N.m.s, i.e. shoulder torque x time expressed as Newton meter seconds, and the endurance time was 4.3 (SD 1.20) min. The rms-EMG as well as the LDF increased significantly during endurance, both when related to endurance time and to amount of load. The MPF showed no significant changes. The mean total increase in muscle blood flow was 175% of that recorded in the initial rest period. The average increase per each 10 s of contraction was 2.9%. Maximum was reached during the 1st min of recovery followed by a fall to the base level that was reached within 77 s on average. The amount of load produced and the blood flow increase was smaller than that found in a separate study of men, indicating a lower functional capacity.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7671881

Larsson, S E; Cai, H; Zhang, Q; Larsson, R; Oberg, P A

1995-01-01

376

Laser Doppler Imaging para quantificação do fluxo sanguíneo de polpa digital em condições basais e após estímulo frio em pacientes com esclerose sistêmica Quantification of basal digital blood flow and after cold stimulus by laser doppler imaging in patients with systemic sclerosis  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Determinar o comportamento dinâmico do fluxo sanguíneo da microcirculação digital, antes e após dois estímulos frios (EF de diferentes intensidades, utilizando o método do Laser Doppler Imaging (LDI em pacientes com esclerose sistêmica (ES e controles saudáveis. MÉTODOS: Foram incluídos 14 pacientes com ES (51,2 ± 5,5 anos de idade e 12 controles saudáveis (44,8 ± 9,9 anos. Foram realizados dois protocolos alternativos de EF (submersão das mãos em água a 10 ºC ou 15 ºC, durante 1 minuto. O fluxo médio das quatro polpas digitais da mão esquerda (FPD foi mensurado com a utilização do LDI (Moor LDI-VR, em condições basais, nos períodos de 1, 4, 10, 25 e 40 minutos após EF. RESULTADOS: O fluxo basal foi significativamente menor em ambos os protocolos em pacientes com ES comparados a controles (312,9 ± 102,7 versus 465,4 ± 135,4 PU, P = 0,006, no protocolo a 15 ºC; 305,2 ± 121,0 versus 437,9 ± 119,8 PU, P = 0,01, no protocolo a 10 ºC. Nos controles houve declínio significativo do FPD após EF, em comparação aos valores basais apenas no tempo de um minuto após EF a 15 ºC (P = 0,001 e nos tempos de 1 e 25 minutos após EF a 10 ºC (P = 0,005; P = 0,001, respectivamente. Nos pacientes com ES, houve declínio significativo do FPD nos tempos de 1, 4 e 10 minutos após ambos EFs (P OBJECTIVES: The objective of this study was to investigate the dynamic behavior of the blood flow of the microvascular circulation of the fingertips before and after two cold stimuli (CS, using Laser Doppler Imaging with different intensities in patients with systemic sclerosis (SSc and in healthy individuals. PATIENTS AND METHODS: Fourteen SSc patients (51.2 ± 5.5 years with Raynaud's phenomenon and 12 healthy controls (44.8 ± 9.0 years were included in this study. Two CS protocols (submersion of the hands in water at 10 ºC or 15 ºC for 1 minute were performed on the same day. Mean fingertip blood flow (FBF of four digits of the left hand was measured using LDI (Moor LDI-VR, Moor Instruments at baseline and at 1, 4, 10, 25, and 40 minutes after CS. RESULTS: Baseline blood flow was significantly lower in both CS protocols in SSc patients when compared to controls (312.9 ± 102.7 vs 465.4 ± 135.4 PU, P = 0.006 at 15 ºC; 305.2 ± 121.0 vs 437.9 ± 119.8 PU; P = 0.01 at 10 ºC. In the control group, a significant decrease in FBF after CS, when compared to baseline, was observed 1 minute (P = 0.001 after CS at 15 ºC and at 1 (P = 0.005 and 25 minutes (P = 0.001 after CS at 10 ºC. In SSc patients, a significant decrease in FBF was observed in both CS protocols at 1, 4, and 10 minutes (P < 0.000; P = 0.002; P = 0.014, after CS at 15 ºC; P < 0.000; P = 0.004; P = 0.001, after CS at 10 ºC. CONCLUSIONS: Laser Doppler Imaging showed lower baseline fingertip perfusion and further reduction after CS in SSc patients compared to controls. Quantification of fingertip blood flow by LDI may be useful in the longitudinal monitoring of the disease status and therapeutic interventions in SSc.

Marcelo José Uchoa Corrêa

2010-04-01

377

Realization of a multipath ultrasonic gas flowmeter based on transit-time technique.  

Science.gov (United States)

A microcomputer-based ultrasonic gas flowmeter with transit-time method is presented. Modules of the flowmeter are designed systematically, including the acoustic path arrangement, ultrasound emission and reception module, transit-time measurement module, the software and so on. Four 200 kHz transducers forming two acoustic paths are used to send and receive ultrasound simultaneously. The synchronization of the transducers can eliminate the influence caused by the inherent switch time in simple chord flowmeter. The distribution of the acoustic paths on the mechanical apparatus follows the Tailored integration, which could reduce the inherent error by 2-3% compared with the Gaussian integration commonly used in the ultrasonic flowmeter now. This work also develops timing modules to determine the flight time of the acoustic signal. The timing mechanism is different from the traditional method. The timing circuit here adopts high capability chip TDC-GP2, with the typical resolution of 50 ps. The software of Labview is used to receive data from the circuit and calculate the gas flow value. Finally, the two paths flowmeter has been calibrated and validated on the test facilities for air flow in Shaanxi Institute of Measurement & Testing. PMID:23809902

Chen, Qiang; Li, Weihua; Wu, Jiangtao

2014-01-01

378

Electromagnetic Borehole Flowmeter Testing in R-Area  

Energy Technology Data Exchange (ETDEWEB)

Six constant-rate, multiple-well aquifer tests were recently conducted in R-area to provide site-specific in situ hydraulic parameters for assessing groundwater flow and contaminant transport models of R-Reactor Seepage Basins (RRSB) plume migration and RRSB remedial alternatives. The pumping tests were performed in the Upper Three Runs and Gordon aquifers between December 1999 and February 2000. The tests provide reliable estimates of horizontal conductivity averaged over aquifer thickness, and a relatively large horizontal zone of influence. To complement these results, Electromagnetic Borehole Flowmeter (EBF) testing was subsequently performed to determine the vertical variation of horizontal conductivity for RPC-2PR, RPC-3PW, RPT-2PW, RPT-3PW, RPT-4PW and RPT-30PZ. The EBF data generally indicate significant aquifer heterogeneity over the tested screen intervals (Figures 14, 16-18, 20, 22, 24, 26 and 27-31). The vertical variation of groundwater flow in or out of the well screen under ambient conditions was also measured (Figures 13, 15, 19, 21, 23 and 25). These data have implications for contaminant monitoring.

Flach, G.P.

2000-10-12

379

Development of a Digital and Battery-Free Smart Flowmeter  

Directory of Open Access Journals (Sweden)

Full Text Available To effectively manage and save energy and natural resources, the measurement and monitoring of gas/fluid flows play extremely important roles. The objective of this study was to incorporate an efficient power generation and a power management system for a commercial water flow meter thus eliminating the usage of batteries. Three major technologies have made this possible: a low power consumption metering unit, a cog-resistance-free generator with high efficiency; and an effective methodology to extract/store energy. In this system, a new attempt and simple approach was developed to successfully extract a portion of the kinetic energy from the fluid/air, store it in a capacitor and used it efficiently. The resistance to the flow was negligible because of the very low power consumption as well as the application of the coreless generator technology. Feasibility was demonstrated through repeated experiments: for air flowing in an 11 mm diameter pipe, 18 s of energy harvesting at 10 revolution-per-second (RPS turbine speeds generated enough power for the flowmeter to operate for 720 s with a flowrate of 20 RPS, without battery or any external power. The pipeline monitoring in remote areas such as deep sea oil drilling; geothermal power plants and even nuclear power plants could benefit greatly from this self-power metering system design.

Wang Song Hao

2014-06-01

380

Error Characteristics of Clamp-on Ultrasonic Flowmeters Depending on Location of Sensors and Downstream Straight Run of Bent Pipe  

International Nuclear Information System (INIS)

Flowmeters that measure the amount of fluid passing through conduits must kept accurate by comparison and the periodic calibration. The reference meters used are clamp-on meters that mount sensors on the outer wall of the pipe. They are called 1-path, 2-path or 4-path flowmeters depending on the number of sensors. We selected a flowmeter mainly used for K-water as test a flowmeter. We carried out experiments to find the intrinsic error of the flowmeter and errors in the downstream of a double bent pipe. The results show that there are the sensor locations that meet the tolerance. We suggested the angle of the sensor, the straight run from the downstream of the bent pipe and the number of sensors. So it is possible to improve the water treatment process and increase the accounted water rate by upgraded flow measurement technology

2011-08-01

 
 
 
 
381

Flow Velocities After Carotid Artery Stenting: Impact of Stent Design. A Fluid Dynamics Study in a Carotid Artery Model with Laser Doppler Anemometry  

International Nuclear Information System (INIS)

Purpose. To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. Methods. Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 ?m. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. Results. The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. Conclusions. Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow behavior. Depending on the stent design the flow alterations are located in different regions. All the stents tested were suitable for the carotid bifurcation. The MembraX prototype has shown promising hemodynamic properties ex vivo

2005-01-01

382

An additional uncertainty of the throughput generated by the constant pressure gas flowmeter  

International Nuclear Information System (INIS)

The lower range limit of constant pressure gas flowmeters is about 10-8 Paxm3/s. Detrimental gas throughputs caused by leaks and gassing from surfaces prevent from its decrease. Even if the flowmeter is entirely vacuum tight the throughput caused by the outgassing from surfaces can be sufficiently reduced only by pumping at elevated temperature. It can be performed with the flowmeters using directly driven bellows or diaphragm bellows in the volume displacers. Despite it, the lower range limit can hardly be decreased more than several ten times with up to now known designs. An additional uncertainty caused by the difference in pressure at the initial and final instant of measurement will increase at generating small throughputs to the extent that it will kill the measurement

2008-03-01

383

An additional uncertainty of the throughput generated by the constant pressure gas flowmeter  

Energy Technology Data Exchange (ETDEWEB)

The lower range limit of constant pressure gas flowmeters is about 10{sup -8} Paxm{sup 3}/s. Detrimental gas throughputs caused by leaks and gassing from surfaces prevent from its decrease. Even if the flowmeter is entirely vacuum tight the throughput caused by the outgassing from surfaces can be sufficiently reduced only by pumping at elevated temperature. It can be performed with the flowmeters using directly driven bellows or diaphragm bellows in the volume displacers. Despite it, the lower range limit can hardly be decreased more than several ten times with up to now known designs. An additional uncertainty caused by the difference in pressure at the initial and final instant of measurement will increase at generating small throughputs to the extent that it will kill the measurement.

Peksa, L; Gronych, T; Repa, P; Wild, J [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Praha 8 (Czech Republic); Tesar, J; Prazak, D; KrajIcek, Z; Vicar, M [Czech Institute of Metrology, OkruznI 31, 638 00 Brno (Czech Republic)], E-mail: ladislav.peksa@mff.cuni.cz

2008-03-01

384

A validated model for the electromagnetic flowmeter's measuring cell  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes as well a measurement model for the electromagnetic flowmeter's measuring cell that constitutes an off-line measurement model for the electromagnetic flowmeter with which it is possible to try different signal processing algorithms to estimate the flowrate value. This model was validated using impedance spectroscopy and spectrometry. Knowing the value of the electrode/electrolyte impedance it is possible as well to determine the value of the input impedance of the preamplifier that reduces the error caused by the impedance of the electrode/electrolyte interface. The value of this latter is used on the other hand to determine the value of the lower frequency limit above which the reading of the induced voltage level of the electromagnetic flowmeter can be carried out with a satisfactory signal-to-noise ratio. (orig.)

Maaiouf, A.I. [Dargroup, Verdun (Lebanon)

2006-06-15

385

Note: Ultrasonic gas flowmeter based on optimized time-of-flight algorithms  

Science.gov (United States)

A new digital signal processor based single path ultrasonic gas flowmeter is designed, constructed, and experimentally tested. To achieve high accuracy measurements, an optimized ultrasound driven method of incorporation of the amplitude modulation and the phase modulation of the transmit-receive technique is used to stimulate the transmitter. Based on the regularities among the received envelope zero-crossings, different received signal's signal-to-noise ratio situations are discriminated and optional time-of-flight algorithms are applied to take flow rate calculations. Experimental results from the dry calibration indicate that the designed flowmeter prototype can meet the zero-flow verification test requirements of the American Gas Association Report No. 9. Furthermore, the results derived from the flow calibration prove that the proposed flowmeter prototype can measure flow rate accurately in the practical experiments, and the nominal accuracies after FWME adjustment are lower than 0.8% throughout the calibration range.

Wang, X. F.; Tang, Z. A.

2011-04-01

386

Note: Ultrasonic gas flowmeter based on optimized time-of-flight algorithms  

Energy Technology Data Exchange (ETDEWEB)

A new digital signal processor based single path ultrasonic gas flowmeter is designed, constructed, and experimentally tested. To achieve high accuracy measurements, an optimized ultrasound driven method of incorporation of the amplitude modulation and the phase modulation of the transmit-receive technique is used to stimulate the transmitter. Based on the regularities among the received envelope zero-crossings, different received signal's signal-to-noise ratio situations are discriminated and optional time-of-flight algorithms are applied to take flow rate calculations. Experimental results from the dry calibration indicate that the designed flowmeter prototype can meet the zero-flow verification test requirements of the American Gas Association Report No. 9. Furthermore, the results derived from the flow calibration prove that the proposed flowmeter prototype can measure flow rate accurately in the practical experiments, and the nominal accuracies after FWME adjustment are lower than 0.8% throughout the calibration range.

Wang, X. F.; Tang, Z. A. [Department of Electronic Science and Technology, Dalian University of Technology, Dalian, 116023 (China)

2011-04-15

387

Ultrasonic flow-metering of low pressure gas transport with high turn-down ratios  

Energy Technology Data Exchange (ETDEWEB)

High-rangeability flow-metering of gaseous media in large conduits under low pressure is a difficult task to be accomplished by a single measuring instrument. In conjunction with an R and D-activity that looked into the possibilities of using contrapropagating ultrasonic transit time method to measure low pressure gas transport at very low and very high velocities, a system was developed with a single pair of transducers. The so developed system has accomplished the task of high-rangeability gas flow-metering at low pressures using special signal processing techniques and unconventional orientations of the transducers to each other and to the direction of flow. The system under discussion has been tested on various offshore platforms. This paper presents test results and assesses the performance of this new ultrasonic gas flowmeter.

Mylvaganam, K.S.

1989-03-01

388

Progress in Doppler instrumentation  

International Nuclear Information System (INIS)

Much progress has been made during the past two decades in the development and use of Doppler ultrasound in medical diagnosis. Doppler instruments have proven to be sensitive to blood dynamics while remaining simple to use and readily available. Future Doppler devices should provide even more information and improved clinical accuracy

1984-01-01

389

Permeability profiles in granular aquifers using flowmeters in direct-push wells  

Science.gov (United States)

Numerical hydrogeological models should ideally be based on the spatial distribution of hydraulic conductivity (K), a property rarely defined on the basis of sufficient data due to the lack of efficient characterization methods. Electromagnetic borehole flowmeter measurements during pumping in uncased wells can effectively provide a continuous vertical distribution of K in consolidated rocks. However, relatively few studies have used the flowmeter in screened wells penetrating unconsolidated aquifers, and tests conducted in gravel-packed wells have shown that flowmeter data may yield misleading results. This paper describes the practical application of flowmeter profiles in direct-push wells to measure K and delineate hydrofacies in heterogeneous unconsolidated aquifers having low-to-moderate K (10-6 to 10-4 m/s). The effect of direct-push well installation on K measurements in unconsolidated deposits is first assessed based on the previous work indicating that such installations minimize disturbance to the aquifer fabric. The installation and development of long-screen wells are then used in a case study validating K profiles from flowmeter tests at high-resolution intervals (15 cm) with K profiles derived from multilevel slug tests between packers at identical intervals. For 119 intervals tested in five different wells, the difference in log K values obtained from the two methods is consistently below 10%. Finally, a graphical approach to the interpretation of flowmeter profiles is proposed to delineate intervals corresponding to distinct hydrofacies, thus providing a method whereby both the scale and magnitude of K contrasts in heterogeneous unconsolidated aquifers may be represented. Journal compilation ?? 2010 National Ground Water Association.

Paradis, D.; Lefebvre, R.; Morin, R. H.; Gloaguen, E.

2011-01-01

390

Flow measurement in bubbly and slug flow regimes using the electromagnetic flowmeter developed  

International Nuclear Information System (INIS)

In order to investigate the characteristics of electromagnetic flowmeter in two-phase flow, an AC electromagnetic flowmeter was designed and manufactured. In various flow conditions, the signals and noises from the flowmeter were obtained and analyzed by comparison with the observed flow patterns with a high speed CCD camera. The experiment with the void simulators in which rod shaped non-conducting material was used was carried out to investigate the effect of the bubble position and the void fraction on the flowmeter. Based on the results from the void simulator, two-phase flow experiments encompassed from bubbly to slug flow regime were conducted. The simple relation ?UTP= ?USP/(1-?) was verified with measurements of the potential difference and the void fraction. Due to the lack of homogeneity in a real two-phase flow, the discrepancy between the relation and the present measurement was slightly increased with void fraction and also liquid volumetric flux jf. Whereas there is no difference in the shape of the raw signal between single-phase flow and bubbly flow, the signal amplitude for bubbly flow is higher than that for single-phase flow at the same water flow rate, since the passage area of the water flow is reduced. In the case of slug flow, the phase and the amplitude of the flowmeter output show dramatically the flow characteristics around each slug bubble and the position of a slug bubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes

2002-11-01

391

Noninvasive linking to a detector in a vortex shedding flowmeter removing the need for a seal  

International Nuclear Information System (INIS)

In many situations it is not easy to connect directly to sensors in hostile and enclosed environments. Problems can arise with the means for providing power to an active sensor and of extracting the information from the sensor. A novel method of electromagnetic linking has been devised for energizing a thermistor and sensing its resistance variations when the thermistor is in a vortex shedding flowmeter. The method does not require any direct electrical connection to be made through the walls of the flowmeter pipe. Design details and performance characteristics are given in the paper

1986-01-01

392

Doppler-free Laser Spectroscopy  

Science.gov (United States)

Instructional material presented at W34 at the Beyond the First Year Laboratory conference and part of W36 âAdvanced & Intermediate Laboratoriesâ at the 2012 AAPT summer meeting. A laboratory manual, a complete list of equipment needed, and experimental tips are included. The main goals for the experiments are: ⢠To measure hyperfine splitting of atomic energy levels in 87Rb. ⢠To become familiar with optical techniques ⢠To become familiar with Michelson interferometry and measurement calibration

Hudek, Laboratory P.

2013-02-13

393

Arm locking with Doppler estimation errors  

International Nuclear Information System (INIS)

At the University of Florida we developed the University of Florida LISA Interferometer Simulator (UFLIS) in order to study LISA interferometry with hardware in the loop at a system level. One of the proposed laser frequency stabilization techniques in LISA is arm locking. Arm locking uses an adequately filtered linear combination of the LISA arm signals as a frequency reference. We will report about experiments in which we demonstrated arm locking using UFLIS. During these experiments we also discovered a problem associated with the Doppler shift of the return beam. The initial arm locking publications assumed that this Doppler shift can perfectly be subtracted inside the phasemeter or adds an insignificant offset to the sensor signal. However, the remaining Doppler knowledge error will cause a constant change in the laser frequency if unaccounted for. Several ways to circumvent this problem have been identified. We performed detailed simulations and started preliminary experiments to verify the performance of the proposed new controller designs.

2010-05-01

394

Using flowmeter pulse tests to define hydraulic connections in the subsurface: A fractured shale example  

Science.gov (United States)

Cross-borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system. This technique is an improvement over other cross-borehole techniques because measurements can be made in open boreholes without packers or previous identification of water-producing intervals. The method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network. In this method, a hydraulic stress is applied to a borehole connected to a single, permeable fracture, and the distribution of flow induced by that stress monitored in adjacent boreholes. The transient flow responses are compared to type curves computed for several different types of fracture connections. The shape of the transient flow response indicates the type of fracture connection, and the fit of the data to the type curve yields an estimate of its transmissivity and storage coefficient. The flowmeter pulse test technique was applied in fractured shale at a volatile-organic contaminant plume in Watervliet, New York. Flowmeter and other geophysical logs were used to identify permeable fractures in eight boreholes in and near the contaminant plume using single-borehole flow measurements. Flowmeter cross-hole pulse tests were used to identify connections between fractures detected in the boreholes. The results indicated a permeable fracture network connecting many of the individual boreholes, and demonstrated the presence of an ambient upward hydraulic-head gradient throughout the site.

Williams, J. H.; Paillet, F. L.

2002-01-01

395

Coupled Lagrangian and Eulerian simulation of bubbly flows in vertical pipes: validation with experimental data using multi-sensor conductivity probes and laser doppler anemometry  

International Nuclear Information System (INIS)

Understanding the dynamics of multiphase systems is an issue of particular interest in the field of Computer Fluid Dynamics (CFD) applied to Nuclear Reactor Safety. A better knowledge of the forces that act on the bubbles moving in a continuous turbulent random fluid field is of importance for a complete description of the bubble's motion and to obtain for instance the radial and axial void fraction distribution inside the reactor channels. Experiments specifically designed to understand the forces that act on the bubbles are a tool necessary to validate the models implemented inside the CFD codes. With this goal in mind, an upward isothermal co-current air-water flow in a vertical pipe (52 mm inner diameter) has been experimental investigated. Local measurements of void fraction, interfacial area concentration (IAC), interfacial velocity and Sauter mean diameter were measured using a four sensor conductivity probe. Liquid velocity and turbulence intensity were also measured using Laser Doppler Anemometry (LDA). Different air-water flow configurations were investigated for a liquid flow rate ranged from 0.491 m/s to 3 m/s and a void fraction up to 25 pc. For each two-phase flow configuration twenty five radial position and three axial locations were measured by the conductivity probe methodology, and several radial profiles were also measured with LDA at different axial positions. Numerical simulations of these experiments for bubbly flow conditions were performed by coupling a Lagrangian code that tracks the 3D motion of the individual bubbles in cylindrical coordinates (r, ?, Z) inside the fluid field under the action of the following forces: buoyancy, drag, lift, and wall lubrication. Also we incorporate a 3D stochastic differential equation model to account for the random motion of the individual bubbles in the turbulent velocity field of the carrier liquid. This type of models denoted as continuous random walk models are used to predict the turbulent diffusion of the bubbles in the fluctuating velocity field of the carrier fluid. Also we have considered the deformation that suffers the bubbles when they touch the walls of the pipe and are compressed until they rebound. The velocity and turbulence fields of the liquid phase were computed by solving the time dependent mass, energy, and momentum conservation equations in its Reynolds Averaged Transport Equation form (RANS). The turbulent kinetic energy k, and the dissipation rate ? transport equations were simultaneously solved by using the k, epsilon model or the renormalized group model (RNG) model in a (r,z) grid by the finite volume method using the SIMPLER algorithm. Both Lagrangian and Eulerian calculations were performed in parallel because when integrating the 3D stochastic differential equations that take into account the motion of the bubbles in the fluid field we must consider the effect of the turbulence on the bubble's motion. To do this we must know the turbulence field that feels the bubble at each position along the path trajectory. Good predictions were obtained for the bubbles trajectories and the void fraction distribution in the channels when we consider that the lift radial force depends on the bubble's size and the bubbles are distorted, expressing this deformation in terms of the Eoetvos number. (authors)

2012-01-23

396

Free water level electromagnetic flowmeter in wide use; Himansuiyo denji ryuryokei no tekiyo han`i kakudai  

Energy Technology Data Exchange (ETDEWEB)

Free water level electromagnetic flowmeter is in wide use for accurate measurement of discharge flow rates or natural flow rates in pipe channels or open channels of trunk sewerage. However, since its application was limited due to a narrow aperture range of 150-300mm, the new flowmeter up to 600mm applicable to measurement of flow rates of trunk sewerage was developed, and put on the market in July 1998. Hereafter, these flowmeters are expected to be widely applied to appropriate operation of regional sewerage through accurate measurement of inflow and outflow in each district, and operation control of pumping stations and sewage treatment plants. (translated by NEDO)

NONE

1999-03-01

397

Development, Calibration and Deployment of an Electromagnetic Flowmeter for Cross-Hole Hydrogeologic Experiments  

Science.gov (United States)

We developed an autonomous electromagnetic flowmeter as part of a cross-hole hydrogeologic experiment using subseafloor borehole observatories (CORKs) that penetrate into the volcanic ocean crust. The cylindrical flowmeter is adapted from a conventional industrial tool and hardened for use at water depths up to 6000 m. In addition, the electronics were modified with a new power controller, and a data logger and communication board was added to enable data storage and long-term, autonomous use for up to eight years. The flowmeter generates a magnetic field and measures a voltage gradient that is created across the orifice as water moves through it. This kind of tool is ideally suited for use in the deep sea, particularly for measuring hydrothermal fluids emanating from the ocean crust, because it requires no moving parts, places no obstructions along the flow path, gives total flow volume as well as instantaneous flow rate, and is highly accurate across a large dynamic range, including bi-directional flow. This flowmeter was deployed on a CORK wellhead using an adapter and ring clamp system located above a 4-inch ball valve. The ball valve can be opened to permit flow (from an overpressured formation) out of the CORK and into the overlying ocean. A polyvinyl chloride "chimney" positioned vertically above the flowmeter is instrumented with autonomous temperature loggers to permit an additional estimate of fluid flow rates with time, based on heat loss during fluid ascent, and to facilitate fluid sampling. Calibration of the new flowmeter was completed in two stages: tank testing using a pump at flow rates of 0.5 to 1.2 L/s, and by lowering the flowmeter on a wireline at sea at rates equivalent to 0.5 to 5.2 L/s. A cross plot of apparent and reference flow rates obtained during calibration indicates a highly linear instrument response. Comparison of instantaneous (once per minute) and integrated (total flow) data collected during calibration indicates good agreement, although the instantaneous data tended to be noisy because of irregularity of flow (turbulence). The flowmeter was deployed in Summer 2011 on a CORK installed in IODP Hole 1362B, on the eastern flank of the Juan de Fuca ridge. Once the flowmeter was attached to the wellhead, the underlying ball valve was opened, which allowed overpressured fluids from the permeable ocean crust to flow upward and out of the seafloor at 5 to 10 L/s (estimated rate). Changes in formation fluid pressure resulting from this flow are being monitored in four additional CORKs located 310 to 2320 m away from Hole 1362B, which will allow large-scale, directional assessment of formation properties. The flowmeter is recording data for instantaneous flow rate and total flow once per hour, and will be recovered to permit collection and analysis of experimental data during a servicing visit in Summer 2012.

Slovacek, A. E.; Fisher, A. T.; Kirkwood, W.; Wheat, C. G.; Maughan, T.; Gomes, K.

2011-12-01

398

Doppler lidar atmospheric wind sensor - Reevaluation of a 355-nm incoherent Doppler lidar  

Science.gov (United States)

Reliable Nd:YAG laser technology and currently available optical sensors are presently used to reevaluate the performance of an incoherent Doppler lidar system operating at 354.7 nm. This system makes a more efficient use of output laser power than heretofore possible through a matching of the usable and detectable field of view of the Fabry-Perot interferometer receiver with that of the transmitter. Major advantages accrue to this system from the lower output power requirement, which is a primary cost driver for the prospective Spaceborne Doppler Wind Lidar.

Rees, David; Mcdermid, I. Stuart

1990-01-01

399

Doppler Shift Target Localization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper outlines the problem of doppler-based target position and velocity estimation using a sensor network. The minimum number of doppler shift measurements at distinct generic sensor positions to have a finite number of solutions, and later, a unique solution for the unknown target position and velocity is stated analytically. Furthermore, we study the same problem where not only doppler shift measurements are collected, but also other types of measurements are available, e.g. bearing o...

2013-01-01