WorldWideScience
 
 
1

Laser double Doppler flowmeter  

Science.gov (United States)

The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

2014-05-01

2

Compact laser Doppler choroidal flowmeter  

Science.gov (United States)

A compact instrument is described that allows the measurement of the laser Doppler flow parameters, i.e., the velocity, the volume, and flow of blood in the foveal region of the human choroidal vascular system. This new device uses the optical principle of confocality for the delivery of the laser light to the site of measurement and heterodyne detection of the Doppler frequency shifted scattered light. Power of the incident light (785 nm) at the cornea is 90 (mu) W. Measurements were obtained in both eyes of a group of 21 normal volunteers without pupil dilatation. We determined the intrasubject reproducibility and the minimum statistically significant detectable changes in the flow parameters for a group of 21 eyes (one in each subject). Linear correlations were also established between the flow parameters in the right and left eyes.

Geiser, Martial H.; Diermann, Ulrich; Riva, Charles E.

1999-10-01

3

Helmet-mounted choroidal laser Doppler flowmeter  

Science.gov (United States)

A compact laser Doppler flowmeter (35x80x210mm3) for the measurement of subfoveal choroidal blood flow parameters (ChBF) was mounted on a helmet. This device allows the measurement of ChBF during dynamic exercises or in supine position, without the need for pupil dilatation. Its optical system is based on a Schlieren arrangement by which the surface of light collection and that of the illumination are spatially separated by an obscuration. The laser probing beam ((lambda) equals 790 nm, 100 (mu) W at the cornea) is focused at the fovea by having the tested subject look directly at the beam. Computer analysis of the photocurrent produced by the scattered light provides a relative measure of the mean blood velocity, number and flux of the red blood cells in the choriocapillaris. Measurements were performed to assess the reliability of the flow parameters measurements in normal volunteers: reproducibility and sensibility when subjects are sitting or standing; measurement of changes in ChBF in the case of isometric and dynamic exercises. Results demonstrate that this new helmet-mounted device provides data comparable to the conventional device. It allows for the first time, however, the continuous measurement of choroidal hemodynamics in humans during various types of exercises.

Geiser, Martial H.; Moret, Fabrice; Riva, Charles E.

2001-06-01

4

Application of the laser Doppler flowmeter for measurement of blood pressure and functional parameters of microcirculation.  

Science.gov (United States)

The laser Doppler flowmeter has become an effective tool for the clinical study of microcirculation with non-invasive measurements and excellent velocity resolution. Microcirculation flow measurements cannot be used as reference criteria for circulation function. Thus, the relative change in fingertip microcirculation was measured through inflation and deflation of an automatic sphygmomanometer wrapped around the arm, and the blood pressure and functional parameters of circulation, such as biological zero (BZ), peak flow (PF) and time to peak flow (tp), were determined. For 50 healthy participants, the correlation coefficients for the laser Doppler flowmeter and oscillometric results were 0.950 and 0.838 for systolic and diastolic pressure, respectively. The mean and standard errors for both methods fell within the range specified in the Association for the Advancement of Medical Instrumentation standards. The BZ of an edema patient was about 5 times higher than normal. For patients with peripheral arterial occlusive disease (PAOD), the PF could not be determined, and the tp was about twice the normal value. The accuracy of blood pressure measurements using the laser Doppler flowmeter was comparable to that of the commonly used oscillometric sphygmomanometer, and the physiological circulation functional parameters were useful in identifying signs of edema and PAOD. PMID:23114464

Hu, Chang-Lin; Lin, Zhan-Sheng; Chen, Yen-Yu; Lin, Yuan-Hsiang; Lai, Mei-Feng; Li, Meng-Lin

2012-01-01

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 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)

6

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

Directory of Open Access Journals (Sweden)

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

Meirelles Jr. Roberto Ferreira

2003-01-01

7

Wearable blood flowmeter appcessory with low-power laser Doppler signal processing for daily-life healthcare monitoring.  

Science.gov (United States)

A new appcessory for monitoring peripheral blood flow in daily life consists of a wearable laser Doppler sensor device and a cooperating smart phone application. Bluetooth Low Energy connects them wirelessly. The sensor device features ultralight weight of 15 g and an intermittent signal processing technique that reduces power consumption to only 7 mW at measurement intervals of 0.1 s. These features enable more than 24-h continuous monitoring of peripheral blood flow in daily life, which can provide valuable vital-sign information for healthcare services. PMID:25571431

Kuwabara, K; Higuchi, Y; Ogasawara, T; Koizumi, H; Haga, T

2014-08-01

8

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

Scientific Electronic Library Online (English)

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

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

9

Evaluation of the microcirculation in a sheep island pedicle flap with laser Doppler flowmeter and 99m-Tc-labelled red blood cells  

International Nuclear Information System (INIS)

The aim of the study was experimentally to evaluate the capability and reliability of laser Doppler flowmetry (LDF) in conditions of circulatory deficiency, by correlating it to flow-related parameters measured by a radionuclide-imaging technique and using 99m-Tc red blood cells (RBCs). For this purpose, a pedicle island flap in the sheep was used, with well-perfused proximal parts and with evident stasis in the distal third of the flap. No correlation was found between results obtained with the two techniques. In regions with evident stasis, falsely high LDF readings were recorded. This may be due to a back-and-forth motion of the RBCs under the probe, rather than to true flow. It was concluded that, while LDF seems reliable in detecting complete arterial occlusion, it is unreliable in predicting either complete venous occlusion or partial obstruction of the flow to and from the flap. Clinical use for this purpose cannot be recommended

10

On the Accuracy Evaluation of Ultrasonic Doppler Flowmeter  

International Nuclear Information System (INIS)

The accuracy evaluation of a pipe flowmeter using ultrasonic velocity profiler is investigated theoretically and experimentally. The error depends basically on the data points on discretized velocity profile, but it decreases rapidly with increasing the data points. It can be reduced, relative to the theoretical velocity profile, below 1% with about 100 data points. The error arising from averaging the instantaneous flow rate increases with the fluctuation amplitude in the loop and decreases with its frequency and total measurement time. A procedure to determine the total averaging time is proposed. (authors)

11

Laser Doppler blood flowmetry  

International Nuclear Information System (INIS)

Laser Doppler flowmetry is a method for continuous quantification of microvascular perfusion. During the measurements, low energy helium-neon laser light is applied to the tissue. Doppler shifted light reflected out of the tissue is then analyzed, and the shift of frequency quantitated. The output signal is proportional to the flux of blood cells in the measuring tissue of some few mm3. Laser Doppler flowmetry can easily be applied for measurements on skin and surgically exposed surfaces. Measurements can also be obtained through an endoscope. Measuring probes of diameter 0.5 mm can be introduced into tissues to quantitate microvascular perfusion within tissues. The article reviews the theory of laser Doppler flowmetry measurements, presents methodological aspects, and gives examples of clinical application. 20 refs., 4 figs

12

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.)

13

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

14

Choroidal blood flow by laser Doppler flowmetry  

Science.gov (United States)

A method is described that provides measurements of blood flow (ChBF) in discrete regions of the choroidal vascular system. It is based on the technique of laser Doppler flowmetry (LDF). A diode laser beam (wavelength equals 810 nm, 60 (mu) W at the cornea) is delivered to the eye through a fundus camera. Light scattered by red blood cells in the tissue volume illuminated by the incident laser beam is detected at the fundus image plane of the camera by an optical fiber. Two analysis schemes of the Doppler signal are developed: one uses commercial skin blood flowmeters and the other a NeXTstation (Motorola 68040 based) computer system. Responses of ChBF to various stimuli are in good agreement with previously published findings in animals. LDF is a valid technique for obtaining noninvasive, continuous, and sensitive recordings of ChBF at discrete regions of the cat eye and in the foveal region of the human fundus, without the need to dilate the pupil.

Riva, Charles E.; Petrig, Benno L.

1995-03-01

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)

16

Speckles in laser Doppler perfusion imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laser Doppler Flowmetry (LDF) is a noninvasive diagnostic method to measure blood flow in tissue [1]. The technique is based on measuring the Doppler shift induced by moving red blood cells to the illuminating coherent light. A laser Doppler instrument often gives output signals related to the flux, velocity and concentration of the moving blood cells. These parameters are extracted from the power spectrum of the intensity fluctuations produced by a photodetector. There are two types of perfu...

Rajan, Vinayakrishnan

2006-01-01

17

Time-domain algorithm for single-photon laser-Doppler flowmetry at large interoptode spacing in human bone.  

Science.gov (United States)

A new laser-Doppler flowmeter at large interoptode spacing, based on single-photon counting (single-photon laser-Doppler flowmetry [SP-LDF]) and allowing assessment of blood flow deep in bone tissue, is proposed and implemented. To exploit the advantages of the new SP-LDF hardware, a dedicated simple and efficient time-domain algorithm has been developed. The new algorithm is based on the zero-order moment of the power density spectrum of the ad hoc prefiltered photoelectric current. The SP-LDF has been validated by Monte Carlo simulations, as well as by experimental measurements on a bone tissue phantom for optical flowmeters and on human. PMID:25402789

Binzoni, Tiziano; Van De Ville, Dimitri; Sanguinetti, Bruno

2014-10-20

18

Toward the development of a low-cost laser Doppler module for ophthalmic microscopes  

Science.gov (United States)

A laser Doppler module easily integrated into a commercial ophthalmic microscope is proposed. Such setup adds flow measurement capability to standard visual inspection of the fundus. The proposed instrument may provide important clinical information such as the detection of vessel occlusion provided by surgical treatments (i.e. photocoagulation). The measuring system is based on a self-mixing laser diode Doppler flowmeter (SM-DF). Reduced costs, easy implementation and small size represent the main features of SM-DF. Moreover, this technique offers the advantage to have the excitation and measurement beams spatially overlapped, thus both overcoming the alignment difficulty of traditional laser Doppler flowmeter and, well fitting with to limited optical aperture of the pupil. Thanks to an on-board DSP-microcontroller, the optoelectronic module directly estimates the blood flow; USB connection and an ad-hoc developed user-friendly software interface allow displaying the result on a personal computer. Preliminary test demonstrates the applicability of the proposed measuring system.

Cattini, Stefano; Rovati, Luigi

2012-03-01

19

Borescopic Laser Doppler Velocimetry probe  

Science.gov (United States)

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

O'Brien, Kory T.

20

Laser Doppler flowmetry in microvascular surgery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the first part of this thesis, describing clinical and experimental studies, laser Doppler flowmetry is evaluated as diagnostic tool to assess tissue microcirculation after various microvascular operations. The second part concerns the application of laser Doppler flowmetry to investigate and to objectivate the negative effects of cigarette smoking upon the microcirculation under normal circumstances as well as after microvascular operative procedures. Success of plastic ...

Adrichem, L. N. A.

1992-01-01

 
 
 
 
21

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

International Nuclear Information System (INIS)

Highly-accurate measurements are required to control the thermal outputs for reactor feedwater flow rates. Calibration tests for flowmeters such as time-of-flight (TOF) ultrasonic flow meters are conducted to assure their accuracy in measurements at standard loops, where flow profile factors, which adjust measurand to real flow rates, are determined usually by conducting calibration tests under ambient flow conditions. As nuclear power plants are aging, readings of flowmeters for reactor feedwater systems drift due to the changes of flow profiles. The causes of those deviations are affected by the change of wall roughness of inner surface of pipings, and those changes of flow patterns lead to large errors in measurements. Therefore, it is still in suspicion if its high accuracy on adjusting measurand by profile factors is traceable against the national standard, and moreover, we have to consider the difference of flow configuration between the flow standard and measurement position on-site. The difference of facilities for measurement conditions can be considered as the concept of 'Facility Factor' and the 'Profile Factor' is not sufficient for correcting the meter reading. It is so discussed that measurement of velocity profile on-site is essential. We proposed the new type of flowmeter called UdFlow/UDF, ultrasonic pulse-Doppler flowmeter, which can measure instantaneously-determined flow-velocity profiles and eliminate the effect of deviated flow profile from expeceffect of deviated flow profile from expected ideal one. Series of calibration tests of UdFlow were conducted at the national standard loops in Mexico, CENAM (The Centro National de Metrologia) and in USA, NIST (National Institute of Standard and Technology) in order to evaluate the accuracy of the flowmeter. Four ultrasonic transducers are mounted on the surface of stainless steel piping circumferentially with the diameters of 100mm and 200mm to measure four velocity profiles. The calibration tests found a deviation better than 0.3% between the two devices in terms of the average of the values recorded by six rounds of each measurement. From the results of measurement conducted with Reynolds number varied, it was found that the overall average deviation between the two devices was better than 0.3%. (author)

22

Aerosol distribution measurements by laser - Doppler - spectroscopy  

International Nuclear Information System (INIS)

Laser-Doppler-Spectroscopy is used to study particle size distribution, especially sodium aerosols, in the presence of uncondensable gases. Theoretical basis are given, and an experimental technique is described. First theoretical results show reasonably good agreement with experimental data available; this method seems to be a promising one. (author)

23

Optic nerve and choroidal blood flow in humans by laser Doppler flowmetry  

Science.gov (United States)

Laser Doppler flowmetry (LDF) was applied to measure blood flow in discrete regions of the optic nerve head (ONHBF) and in the foveal region of the choroid (ChBF) in humans. LDF is based on the Doppler effect. For its ocular application, a diode laser beam (wavelength equals 810 nm, 60 mW at the cornea) was delivered to the eye through a fundus camera. For ONHBF the beam was directed at regions of the optic disk with no apparent individual vessels. For ChBF in the foveal region subjects were asked to look directly at the beam. Light scattered by red blood cells in the tissue volume illuminated by the incident laser beam was detected at the fundus image plane of the camera by an optical fiber. Two analysis schemes of the Doppler signal were developed: one uses commercial skin blood flowmeters, the other a NeXT station (Motorola 68040 based) computer system. Responses of ONHBF and ChBF to various physiological and pharmacological stimuli were obtained and shown to be in agreement with previously published findings. LDF is a valid technique for obtaining non- invasive, continuous and sensitive recordings of ONHBF and foveal ChBF, the latter without the need to dilate the pupil.

Riva, Charles E.; Petrig, Benno L.; Mendel, Mark J.; Cranstoun, Stephen D.

1995-01-01

24

Fish embryo multimodal imaging by laser Doppler digital holography  

CERN Document Server

A laser Doppler imaging scheme combined to an upright microscope is proposed. Quantitative Doppler imaging in both velocity norm and direction, as well as amplitude contrast of either zebrafish flesh or vasculature is demonstrated.

Verrier, Nicolas; Picart, Pascal; Gross, Michel

2015-01-01

25

Utilization of Laser Doppler Flowmetry and Tissue Spectrophotometry for Burn Depth Assessment Using a Miniature Swine Model.  

Science.gov (United States)

Currently, the diagnosis of burn depth is primarily based on a visual assessment and can be dependent on the surgeons' experience. The goal of this study was to determine the ability of laser Doppler flowmeter combined with a tissue spectrophotometer to discriminate burn depth in a miniature swine burn model. Burn injuries of varying depth, including superficial partial, deep partial, and full thickness, were created in seven Goettingen- Minipigs using an aluminium bar (100 °C), which was applied to the abdominal skin for periods of 1, 3, 6, 12, 30 and 60 seconds with gravity alone. The depth of injury was evaluated histologically using hematoxylin and eosin staining. ?All burns were assessed 3 hours after injury using a device that combines a laser light and a white light to determine blood flow, hemoglobin oxygenation, and relative amount of hemoglobin.?The blood flow (41 vs. 124 arbitrary units AU) and relative amount of hemoglobin (32 vs. 52 AU) were significantly lower in full thickness compared to superficial partial thickness burns.?However, no significant differences in hemoglobin oxygenation were observed between these depths of burns (61 vs. 60%).?These results demonstrate the ability of laser Doppler flowmeter and tissue spectrophotometer in combination to discriminate between various depths of injury in the minipig model suggesting that this device may offer a valuable tool for burn depth assessment influencing burn management. PMID:25487000

Lotter, Oliver; Held, Manuel; Schiefer, Jennifer; Werner, Ole; Medved, Fabian; Schaller, Hans-Eberhard; Rahmanian-Schwarz, Afshin; Jaminet, Patrick; Rothenberger, Jens

2014-12-01

26

Superheterodyne three-component laser Doppler anemometer  

International Nuclear Information System (INIS)

The design, method of tuning and principle of operation of a three-component laser Doppler anemometer with inverse-differential optical train are described. Employment of frequency-type light modulator with a 100% modulation factor permitting smooth variation of light frequency means that the anemometer can operate in superheterodyne mode. The range of measured velocities is within 1 mm/s - 50 m/s. Relative error of velocity measurement in a multi-particle mode was not in excess of 5%. Methodical opportunities of the instrument are demonstrated, using gas velocity field measurement by way of example

27

Laser Doppler velocimetry and its application to turbulent flow measurements  

International Nuclear Information System (INIS)

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

28

Laser radar range profile, Doppler spectra and range resolved Doppler imaging technologies for the target recognition  

Science.gov (United States)

The development of laser range profile, Doppler spectra and Range Resolved Doppler imaging technologies including the experiments, simulations and engineering applications have been summarized and reviewed in this paper. It was analyzed the problems of the laser radar imaging system which need to solve in experiments and models. The achievements and the key technologies of Range profile, Doppler spectra and Range Doppler imaging laser radar are reported in detail. Different typically theoretical simulated models have been built to show the last technologies of target recognition for laser radar in order to be based on the further studying on designing the laser radar imaging systems in many applications and offering the precise data of the detected target.

Wu, Pengfei; Wang, Ming-Jun; Ke, Xi-zheng; Gong, Yan-jun; Teng, Yang

2014-11-01

29

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

30

Widefield laser doppler velocimeter: development and theory.  

Energy Technology Data Exchange (ETDEWEB)

The widefield laser Doppler velocimeter is a new measurement technique that significantly expands the functionality of a traditional scanning system. This new technique allows full-field velocity measurements without scanning, a drawback of traditional measurement techniques. This is particularly important for tests in which the sample is destroyed or the motion of the sample is non-repetitive. The goal of creating ''velocity movies'' was accomplished during the research, and this report describes the current functionality and operation of the system. The mathematical underpinnings and system setup are thoroughly described. Two prototype experiments are then presented to show the practical use of the current system. Details of the corresponding hardware used to collect the data and the associated software to analyze the data are presented.

Hansche, Bruce David; Reu, Phillip L.; Massad, Jordan Elias

2007-03-01

31

Laser Doppler flowmetry in manual medicine research.  

Science.gov (United States)

Laser Doppler flowmetry (LDF) is commonly used in combination with reactivity tests to noninvasively evaluate skin sympathetic nerve activity and skin microvascular function. In manual medicine research, LDF has been used as a marker for global peripheral sympathetic nervous system function, but these results should be considered with caution because skin sympathetic nerve activity physiology is often overlooked. Another limitation of LDF in manual medicine research is the processing of LDF recordings. Two methods have been suggested: the time-domain analysis and the frequency-domain analysis. Standardization is required for data collection and processing in either domain to accurately interpret these changes in skin blood flow that occur after manual procedures. For physiologic studies using LDF, the authors recommend the use of noninvasive reactivity tests (positive controls) to evaluate the different mechanisms involved in overall skin blood flow changes and to compare the magnitude of these changes with those specifically elicited by manual procedures. PMID:25429081

Zegarra-Parodi, Rafael; Snider, Eric J; Park, Peter Yong Soo; Degenhardt, Brian F

2014-12-01

32

Sub-Doppler laser cooling of potassium atoms  

International Nuclear Information System (INIS)

We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25±3 ?K and 47±5 ?K in high-density samples of the two isotopes 39K and 41K, respectively. Our findings should find application to other atomic systems.

33

Application of wavelet analysis in laser Doppler vibration signal denoising  

Science.gov (United States)

Large number of experiments show that, due to external disturbances, the measured surface is too rough and other factors make use of laser Doppler technique to detect the vibration signal contained complex information, low SNR, resulting in Doppler frequency shift signals unmeasured, can not be demodulated Doppler phase and so on. This paper first analyzes the laser Doppler signal model and feature in the vibration test, and studies the most commonly used three ways of wavelet denoising techniques: the modulus maxima wavelet denoising method, the spatial correlation denoising method and wavelet threshold denoising method. Here we experiment with the vibration signals and achieve three ways by MATLAB simulation. Processing results show that the wavelet modulus maxima denoising method at low laser Doppler vibration SNR, has an advantage for the signal which mixed with white noise and contained more singularities; the spatial correlation denoising method is more suitable for denoising the laser Doppler vibration signal which noise level is not very high, and has a better edge reconstruction capacity; wavelet threshold denoising method has a wide range of adaptability, computational efficiency, and good denoising effect. Specifically, in the wavelet threshold denoising method, we estimate the original noise variance by spatial correlation method, using an adaptive threshold denoising method, and make some certain amendments in practice. Test can be shown that, compared with conventional threshold denoising, this method is more effective to extract the feature of laser Doppler vibration signal.

Lan, Yu-fei; Xue, Hui-feng; Li, Xin-liang; Liu, Dan

2010-10-01

34

Muscle activity characterization by laser Doppler Myography  

International Nuclear Information System (INIS)

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

35

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 cular 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)

36

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

International Nuclear Information System (INIS)

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

37

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

38

Holographic laser Doppler imaging of microvascular blood flow  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency shifted reference beam, permits frequency selective imaging in the radiofrequency range. These Doppler images are acquired with an off axis Mach Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral ...

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

2014-01-01

39

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

40

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

 
 
 
 
41

Translational and Brownian motion in laser-Doppler flowmetry of large tissue volumes  

International Nuclear Information System (INIS)

This study reports the derivation of a precise mathematical relationship existing between the different p-moments of the power spectrum of the photoelectric current, obtained from a laser-Doppler flowmeter (LDF), and the red blood cell speed. The main purpose is that both the Brownian (defining the 'biological zero') and the translational movements are taken into account, clarifying in this way what the exact contribution of each parameter is to the LDF derived signals. The derivation of the equations is based on the quasi-elastic scattering theory and holds for multiple scattering (i.e. measurements in large tissue volumes and/or very high red blood cell concentration). The paper also discusses why experimentally there exists a range in which the relationship between the first moment of the power spectrum and the average red blood cells speed may be considered as 'linear' and what are the physiological determinants that can result in nonlinearity. A correct way to subtract the biological zero from the LDF data is also proposed. The findings should help in the design of improved LDF instruments and in the interpretation of experimental data

42

Hetrodyne Laser Tracking at High Doppler Rates  

Science.gov (United States)

In hetrodyne laser tracking of a spacecraft, the incoming laser signal may be significantly offset from the local laser reference, producing a high-frequency beat note that must be accurately counted to produce an accurate phase measurement.

Hellings, R.; Giampieri, G.; Maleki, L.; Tinto, M.; Danzmamm, K.; Hough, J.; Robertson, D.

1994-01-01

43

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

44

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

45

Holographic laser Doppler imaging of microvascular blood flow  

CERN Document Server

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

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

2014-01-01

46

All semiconductor laser Doppler anemometer at 1.55 ?m  

DEFF Research Database (Denmark)

We report to our best knowledge the first all semiconductor Laser Doppler Anemometer (LIDAR) for wind speed determination. We will present the design and first experimental results on a focusing coherent cw laser Doppler anemometer for measuring atmospheric wind velocities in the 10 meters to 300 meters distance range. Especially, we will demonstrate that both the output power as well as the demanding coherence properties required from the laser source can be accomplished by an all semiconductor laser. Preliminary tests at a distance of 40 meters indicate a typical signal to noise ratio of 9 dB. This result is obtained at a clear day with an up-date rate of 12 Hz.

Hansen, Rene Skov; Pedersen, Christian

2008-01-01

47

Portable ocular laser Doppler red blood cell velocimeter  

Science.gov (United States)

A new hand-held bidirectional ocular laser Doppler system for measurement of red blood cell (RBC) velocity in retinal vessels and blood flow in the optic nerve head tissue and in the choriocapillaris is described. Laser power at the cornea is below the maximum permissible level. The instrument is based on the well-established laser Doppler velocimetry/flowmetry techniques. The optical systems for the delivery of the probing laser beam to the eye fundus and bidirectional detection of the light scattered by the RBCs have been implemented in a portable Kowa Genesis fundus camera. In vitro experiments demonstrate the performance of the instrument and in vivo measurements illustrate the feasibility of retinal blood velocity and choriocapillaris blood flow measurements in awake volunteers.

Logean, E.; Geiser, M. H.; Petrig, B. L.; Riva, C. E.

1997-07-01

48

Vibration measurement by a laser Doppler displacement meter  

Science.gov (United States)

The Laser Doppler Displacement Meter (LDDM), has been applied for the measurement of structure dynamics, such as resonance frequency, Bode plot, settling time, etc. in machine tools, rotary machinery, XY-stages, and servo controls. Other applications are in micromachining and in hard disk drive, such as flight height, head gimbal resonance, runout, etc. The basic principle of the LDDM, its comparison to laser interferometer and also vibrometer, major features and application are described.

Liotto, Gianmarco; Wang, Charles P.

1996-08-01

49

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, D.M.

1984-04-12

50

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

51

Coherent Doppler Laser Radar: Technology Development and Applications  

Science.gov (United States)

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

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

2000-01-01

52

Three-dimensional laser cooling at the Doppler limit  

CERN Document Server

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

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

2014-01-01

53

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.

2011-03-01

54

Laser Doppler measurement of rectal mucosal blood flow  

Digital Repository Infrastructure Vision for European Research (DRIVER)

BACKGROUND—Gut mucosal blood flow measurement is used to study a variety of disorders and possibly extrinsic neural function.?AIMS—To determine optimal measurement criteria and validate this technique as a measure of level of activity of extrinsic autonomic gut innervation.?METHODS—In 26 healthy volunteers a laser Doppler mucosal probe was applied 10 cm from the anus. Response to inhaled salbutamol 200 µg and ipratropium 40 µg, intravenous metoprolol 2.5 mg, and direct sacral...

Emmanuel, A.; Kamm, M.

1999-01-01

55

Sub-Doppler modulation spectroscopy of potassium for laser stabilization  

CERN Document Server

We study modulation spectroscopy of the potassium D2 transitions at 766.7 nm. Heterodyne detection of pump-probe spectroscopy yields sub-Doppler frequency discriminants suitable for stabilizing lasers in experiments with cold atoms. Comparisons are made between spectra obtained by direct modulation of the probe beam, and those using modulation transfer from the pump via nonlinear mixing. Finally, suggestions are made for further optimization of the signals.

Mudarikwa, L; Goldwin, J

2011-01-01

56

Laser Doppler Flowmetry—Development and Clinical Application  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laser Doppler Flowmetry (LDF) is an accurate and reliable method for assessing microcirculatory function. Through a series of in vitro and in vivo experiments, LDF output has been shown to be reproducible and to correlate with bone blood flow as estimated by other methods. The utility of the method in assessing meniscal, tendonous, and ligamentous perfusion has also been demonstrated. LDF has proven potential in clinical research in osteonecrosis, osteomyelitis, fracture healing, and other ar...

Swiontkowski, Marc F.

1991-01-01

57

Reynolds stress measurements in cylindrical geometry using laser Doppler anemometry  

International Nuclear Information System (INIS)

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

58

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...

Risti? Slavica S.; Ili? Jelena T.; ?antrak ?or?e S.; Risti? Ognjen R.; Jankovi? Novica Z.

2012-01-01

59

Holographic laser Doppler imaging of microvascular blood flow  

Science.gov (United States)

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

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

2014-12-01

60

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

 
 
 
 
61

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

62

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

63

Short-time Fourier transform laser Doppler holography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report a demonstration of laser Doppler holography at a sustained acquisition rate of 250 Hz on a 1 Megapixel complementary metal-oxide-semiconductor (CMOS) sensor array and image display at 10 Hz frame rate. The holograms are optically acquired in off-axis configuration, with a frequency-shifted reference beam. Wide-field imaging of optical fluctuations in a 250 Hz frequency band is achieved by turning time-domain samplings to the dual domain via short-time temporal Four...

Samson, Benjamin; Atlan, Michael

2012-01-01

64

Real-time full field laser Doppler imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a full field laser Doppler imaging instrument, which enables real-time in vivo assessment of blood flow in dermal tissue and skin. This instrument monitors the blood perfusion in an area of about 50 cm² 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 microci...

Leutenegger, Marcel; Martin-williams, Erica; Harbi, Pascal; Thacher, Tyler; Raffoul, Wassim; Andre?, Marc; Lopez, Antonio; Lasser, Philippe; Lasser, Theo

2011-01-01

65

Real-time full field laser Doppler imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a full field laser Doppler imaging instrument, which enables real-time in vivo assessment of blood flow in dermal tissue and skin. This instrument monitors the blood perfusion in an area of about 50 cm2 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 microcir...

Leutenegger, Marcel; Martin-williams, Erica; Harbi, Pascal; Thacher, Tyler; Raffoul, Wassim; Andre?, Marc; Lopez, Antonio; Lasser, Philippe; Lasser, Theo

2011-01-01

66

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.)

67

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

68

Holographic laser Doppler imaging of pulsatile blood flow  

CERN Document Server

We report on wide-field imaging of pulsatile motion induced by blood flow using heterodyne holographic interferometry on the thumb of a healthy volunteer, in real-time. Optical Doppler images were measured with green laser light by a frequency-shifted Mach-Zehnder interferometer in off-axis configuration. The recorded optical signal was linked to local instantaneous out-of-plane motion of the skin at velocities of a few hundreds of microns per second, and compared to blood pulse monitored by plethysmoraphy during an occlusion-reperfusion experiment.

Bencteux, Jeffrey; Kostas, Thomas; Bayat, Sam; Atlan, Michael

2015-01-01

69

Laser-Doppler Imaging in the Detection of Peripheral Neuropathy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Small fiber neuropathy is common in a number of systemic diseases and is often challenging to diagnose. Laser-Doppler Imaging (LDI) is a test of small fiber neurovascular function that can quantify the integrity of the vasomotor C-fiber mediated axon-reflex, but no standardized method of analysis exists. We developed a novel LDI analysis technique and tested it in a human model of small fiber neuropathy. Eighteen healthy subjects (age 24±3 years) underwent LDI testing to assess the axon-medi...

Illigens, Ben M. W.; Siepmann, Timo; Roofeh, Joe; Gibbons, Christopher H.

2013-01-01

70

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

71

Electromagnetic flowmeter for dielectric liquids.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Experimental investigation and theoretical analysis of an electromagnetic flowmeter designed for use with dielectric liquids has been carried out. An extensive survey of the industrial users of flowmeters has been made, involving the participation of over 47 companies, which provides information about the current industrial use, attitudes and attributes of electromagnetic and other types of flowmeters. The design of the flowmeter is mainly concerned with overcoming the charge n...

Amare, T.

1995-01-01

72

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 microm, 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. PMID:16642064

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

73

Potential for coherent Doppler wind velocity lidar using neodymium lasers  

Science.gov (United States)

Existing techniques for the frequency stabilization of Nd:YAG lasers operating at 1.06 micron, and the high-gain amplification of radiation at that wavelength, make possible the construction of a coherent Doppler wind velocity lidar using Nd:YAG. Velocity accuracy and range resolution are better at 1.06 micron than at 10.6 microns at the same level of the SNR. Backscatter from the atmosphere at 1.06 micron is greater than that at 10.6 microns by about 2 orders of magnitude, but the quantum-limited noise is higher by 100 also. Near-field attenuation and turbulent effects are more severe at 1.06 micron. In some configurations and environments, the 1.06-micron wavelength may be the better choice, and there may be technological advantages favoring the use of solid-state lasers in satellite systems.

Kane, T. J.; Byer, R. L.; Zhou, B.

1984-01-01

74

Implantable hearing device performance measured by laser Doppler interferometry.  

Science.gov (United States)

Recent application of the Doppler principle laser interferometry to audiology, acoustics and otology has facilitated the development of implantable hearing devices (IHDs). During the design and testing of two different electromagnetic middle ear implants for sensorineural hearing loss, we used single-point laser Doppler interferometry (LDI). A commercially available interferometer, internally calibrated and validated against a National Institute for Standards and Technology (NIST) standard, was used with both mechanical fixtures and fresh temporal bones to evaluate implant mass, shape and orientation, attachment, electromagnetic coupling and acoustic properties. At both Hough Ear Institute and Symphonix Devices, Inc., we have shown that high fidelity and amplitudes can be recorded in vitro over a frequency range of 500 Hz to 10 kHz. These data can provide greater assurance of safety and efficacy to regulatory agencies before entering clinical trials. We propose that LDI be considered as an international standard for accurate, consistent comparison of performances of all IHDs during development. Furthermore, the future availability of human IHD data will allow for the extrapolation of a mechanical bench model of the middle ear transfer function for use in quality control during manufacturing and diagnosis of failure in IHDs. PMID:9170711

Gan, R Z; Wood, M W; Ball, G R; Dietz, T G; Dormer, K J

1997-05-01

75

Fluid Mechanics of Borehole Flowmeters  

Science.gov (United States)

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

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

2005-12-01

76

Laser Doppler flowmetry evaluation of gingival recovery response after laser treatment  

Science.gov (United States)

This study was performed in order to evaluate in vivo the applicability of Laser Doppler Flowmetry (LDF) in recording the gingival blood flow and to assess the changes of gingival blood flow following gingival reshaping performed with Er:YAG and 980 nm diode lasers. The LDF evaluation was performed on 20 anterior teeth, which underwent reshaping of gingiva, corresponding to 5 female patients (4 anterior teeth/patient), aged between 20 and 35. One part of the mouth was treated with Er:YAG laser (LP, VLP modes, 140 - 250 mJ, 10 - 20 Hz, using cylindrical sapphire tips) and other part with 980 nm diode laser (CW, 4 W, contact mode and saline solution cooling). The gingival blood flow was monitored using a MoorLab laser Doppler equipment (Moor Instruments Ltd., Axminster, UK) with a straight optical probe, MP3b, 10 mm. The data were processed using statistical analysis software SPSS v16.0.1. The investigation showed an evident decrease in perfusion for both areas in comparison with the baseline values 24 hours after treatment. The microvascular blood flow increased significantly after 7 days in both areas but mostly in diode area (psurgical treatment of gingival tissue. Moreover, Laser Doppler Flowmetry is adequate for recording changes in gingival blood flow following periodontal surgery.

Todea, Carmen; Cânj?u, Silvana; Dodenciu, Dorin; Miron, Mariana I.; Tudor, Anca; B?l?buc, Cosmin

2013-06-01

77

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

78

[The measurement of cochlear flow by laser Doppler in man: the preliminary results  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laser-Doppler flowmetry is presently one of the methods of choice in measuring cochlear blood flow. The techniques is non-invasive and is based on the frequency shift of the laser beam induced by the red blood cell movement. Previous studies of cochlear blood flow carried out on animals and humans demonstrated the reliability of laser-Doppler flowmetry and its usefulness in understanding inner ear microcirculation physiology. In this paper we present preliminary data obtained from three patie...

Albera, Roberto; Siena, Luigi Francesco

1992-01-01

79

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

80

Short-time Fourier transform laser Doppler holography  

CERN Document Server

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

Atlan, Michael

2012-01-01

 
 
 
 
81

Real-time full field laser Doppler imaging  

Science.gov (United States)

We present a full field laser Doppler imaging instrument, which enables real-time in vivo assessment of blood flow in dermal tissue and skin. This instrument monitors the blood perfusion in an area of about 50 cm2 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. Small animal imaging in mouse ears clearly revealed the network of blood vessels and the corresponding blood perfusion. PMID:21698011

Leutenegger, Marcel; Martin-Williams, Erica; Harbi, Pascal; Thacher, Tyler; Raffoul, Wassim; André, Marc; Lopez, Antonio; Lasser, Philippe; Lasser, Theo

2011-01-01

82

Magnetostriction measurement in thin films using laser Doppler vibrometry  

Science.gov (United States)

This paper reports the laser Doppler vibrometry based measurement of the magnetostriction in magnetic thin films. Using this method, the strain induced by an AC magnetic field in the polycrystalline cobalt ferrite and nickel ferrite thin films grown on silicon and platinized silicon substrates was measured under a DC magnetic bias. The experimental setup and the derivation of the magnetostriction constant from the experimentally measured deflection values are discussed. The magnetostriction values derived using force and bending moment balances were compared with that derived from an industry standard relationship. In addition, we corroborate our approach by comparing the values derived from bending theory calculations of magnetically induced torque to those from measurements using Vibrating Sample Magnetometer (VSM). At high DC magnetic field bias, the magnitude of magnetization calculated from the measured magnetostriction was found to match the measured magnetization by VSM.

Varghese, Ronnie; Viswan, Ravindranath; Joshi, Keyur; Seifikar, Safoura; Zhou, Yuan; Schwartz, Justin; Priya, Shashank

2014-08-01

83

Application of Laser Doppler Vibrometery for human heart auscultation.  

Science.gov (United States)

In this study the potential of a Laser Doppler Vibrometer (LDV) was tested as a non-contact sensor for the classification of heart sounds. Of the twenty participants recorded using the LDV, five presented with Aortic Stenosis (AS), three were healthy and twelve presented with other pathologies. The recorded heart sounds were denoised and segmented using a combination of the Electrocardiogram (ECG) data and the complexity of the signal. Frequency domain features were extracted from the segmented heart sound cycles and used to train a K-nearest neighbor classifier. Due to the small number of participants, the classifier could not be trained to differentiate between normal and abnormal participants, but could successfully distinguish between participants who presented with AS and those who did not. A sensitivity of 80 % and a specificity of 100 % were achieved a test dataset. PMID:25570986

Koegelenberg, S; Scheffer, C; Blanckenberg, M M; Doubell, A F

2014-08-01

84

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 tissue, and in blood absorption. Inhomogeneous models containing small blood vessels, hair, and sweat glands displayed errors 1 mm/s.

Fredriksson, Ingemar; Larsson, Marcus; Strömberg, Tomas

2010-09-01

85

Extremely Shallow Underground Imaging Using Scanning Laser Doppler Vibrometer  

Science.gov (United States)

Ground penetrating radar (GPR) and elastic wave exploration have been widely used in underground exploration. However, it has not been possible to explore extremely shallow underground areas up to 10 cm below the ground surface, because various waves are received and the reflected wave cannot be separated. Although land mines have become a serious problem all over the world, the existing detection methods are not very effective in the case of soil containing electrolytes, for example, laterite soil in Southeast Asia. Therefore, we propose a method using a sound wave and a scanning laser Doppler vibrometer (SLDV). We conducted an exploration experiment of buried objects both in the laboratory and outdoors. As a result, the frequency responses of the buried objects were obtained and the responses of the buried objects were confirmed by imaging. Therefore, it is possible to use this method at an actual site.

Abe, Touma; Sugimoto, Tsuneyoshi

2009-07-01

86

Evaluation of the marginal gingival health using laser doppler flowmetry  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Os objetivos deste estudo foram comparar o fluxo sangüíneo gengival (FSG) em sítios teste (dentes retentores de próteses parciais fixas) e sítios controle (dentes naturais contralaterais) e investigar se há alguma relação entre os índices clínicos (IC) e os valores de FSG. Doze indivíduos saudáveis [...] (6 mulheres e 6 homens) com idades entre 20 a 54 anos participaram deste estudo. O FSG foi medido no ponto médio da gengina marginal em ambos os sítios teste e controle utilizando dopplerfluxometria a laser (DFL). Além disso, as medidas referentes ao índice de placa, índice gengival e profundidade de sondagem foram registradas. Foi observada diferença estatisticamente significante (p0.05) entre os sítios teste e controle com relação aos índices clínicos, exceto para o índice de placa. Os achados deste estudo sugerem que existe uma relação significante entre próteses parciais fixas retidas por resina com margens localizadas subgengivalmente e o FSG marginal. Embora os índices clínicos sejam úteis para coletar informações sobre as condições clínicas dos tecidos gengivais, o FSG é uma ferramenta importante para medir o fluxo sanguíneo tissular gengival e avaliar a saúde periodontal. Em conclusão, a dopplerfluxometria a laser pode ser usada juntamente com índices clínicos para avaliar a saúde gengival marginal. Abstract in english The purposes of this study were to compare the gingival blood flow (GBF) in test sites (teeth retaining fixed partial dentures) and control sites (contralateral natural teeth) and investigate whether there is any relationship between clinical indices and GBF values. Twelve healthy subjects (6 female [...] s and 6 males) aged 20 to 54 years were enrolled this study. The GBF was measured from the middle point of the marginal gingiva in the test and control sites using laser Doppler flowmetry (LDF). Additionally, plaque index, gingival index and probing depth measurements were recorded. Statistically significant difference (p0.05) was found between test and control sites with respect to the clinical indices, except for plaque index. The findings of this study suggest that there is a significant relation between resin-bonded fixed partial dentures with margins located subgingivally and marginal GBF. Clinical indices are helpful to collect information about the clinical health status of gingival tissues, but GBF is a good tool to measure gingival tissue blood flow and assess periodontal health. In conclusion, laser Doppler flowmetry can be used together with clinical indices to evaluate the marginal gingival health.

Hakan, Develioglu; Bülent, Kesim; Aykut, Tuncel.

87

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

88

Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging  

Science.gov (United States)

Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.

Tabatabai, Habib; Oliver, David E.; Rohrbaugh, John W.; Papadopoulos, Christopher

2013-06-01

89

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

90

See the Brain at Work—Intraoperative Laser Doppler Functional Brain Imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

During open brain surgery we acquire perfusion images non-invasively using laser Doppler imaging. The regions of brain activity show a distinct signal in response to stimulation providing intraoperative functional brain maps of remarkably strong contrast.

Martin-williams, Erica J.; Raabe, Andreas; Ville, Dimitri; Leutenegger, Marcel; Szelenyi, Andrea; Hattingen, Elke; Gerlach, Rudiger; Seifert, Voker; Hauger, Christoph; Lopez, Antonio; Leitgeb, Rainer A.; Unser, Michael; Lasser, Theo

2009-01-01

91

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

92

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

DEFF Research Database (Denmark)

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

HØyer, Christian; Sandermann, Jes

2013-01-01

93

High-speed wave-mixing laser Doppler imaging, in vivo.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording with a complementary metal-oxide semi-conductor (CMOS) camera. Observation of a mice cranium with near infrared ($\\lambda$ = 785 nm) laser light in reflection configuration is reported. Doppler spe...

Atlan, Michael; Gross, Michel; Vitalis, Tania; Rancillac, Armelle; Rossier, Jean; Boccara, Claude

2008-01-01

94

Laser doppler flowmetry evaluation as a pulpal vitality test  

International Nuclear Information System (INIS)

The more frequently used pulp vitality tests (PVTs) are the thermal (cold and heat) and the electrical stimulus. These tests are, however, subjective, depending on the sensitivity threshold of each individual, and usually fail when immature or recently traumatised teeth are tested. The laser Doppler flowmetry (LDF) have been suggested as a PVT, by evaluating the pulp measured flow (F). The measured quantity F, used to discriminate healthy and non-vital teeth, is sensitive to factors hardly controlled or predictable, such as the LDFs and probe response differences, and the flow variations among individuals. It was suggested recently a new discriminator, F(%), less sensitive to such factors. The PVTs performances for F (%) and F as discriminators, however, were not known. The present study aimed to evaluate the PVTs' performances using the quantities F(%) and F (dif) as discriminators, both derived from F, and to compare, qualitatively and quantitatively, their performances to that obtained by using F. The quantities F(%) and F(dif) are, respectively, the ratio and the difference of the flow from the interrogated tooth and its healthy homologous, being F(dif) a proposed new discriminator. The obtained confidence intervals (95% of significance) of the areas under ROC curves were from 0,964 to 1,000 for F (%); from 0,959 to 1,000 for F (dif) and; from 0,584 to 0,951 for F; showing that F(%) and F (dif) are more reliable discriminators then F. (author)tors then F. (author)

95

Laser Doppler imaging in the detection of peripheral neuropathy.  

Science.gov (United States)

Small fiber neuropathy is common in a number of systemic diseases and is often challenging to diagnose. Laser Doppler imaging (LDI) is a test of small fiber neurovascular function that can quantify the integrity of the vasomotor C-fiber mediated axon-reflex, but no standardized method of analysis exists. We developed a novel LDI analysis technique and tested it in a human model of small fiber neuropathy. Eighteen healthy subjects (age 24 ± 3 years) underwent LDI testing to assess the axon-mediated flare area in response to 10% acetylcholine iontophoresis. LDI measurements were taken before and longitudinally after a 48-hour application of 0.1% capsaicin (to cause a transient small fiber neuropathy) on the skin of the thigh; placebo cream was placed on the contralateral thigh as a control. We compared our new LDI image analysis technique to two previously published methods. The new LDI analysis technique was the only method to show a consistent difference in axon-reflex area between capsaicin treated and placebo treated skin on all testing days (p<0.05) with maximum attenuation of the flare area immediately post-application (438 ± 298 mm(2) vs. 824 ± 375 mm(2), p<0.05). In conclusion, this study demonstrates that our novel flare area method for LDI analysis can detect neurovascular dysfunction in a model of small fiber neuropathy, is an improvement over existing methods, and may supplement clinical assessment of small fiber neuropathy. PMID:23850386

Illigens, Ben M W; Siepmann, Timo; Roofeh, Joseph; Gibbons, Christopher H

2013-10-01

96

Laser-Doppler Imaging in the Detection of Peripheral Neuropathy  

Science.gov (United States)

Small fiber neuropathy is common in a number of systemic diseases and is often challenging to diagnose. Laser-Doppler Imaging (LDI) is a test of small fiber neurovascular function that can quantify the integrity of the vasomotor C-fiber mediated axon-reflex, but no standardized method of analysis exists. We developed a novel LDI analysis technique and tested it in a human model of small fiber neuropathy. Eighteen healthy subjects (age 24±3 years) underwent LDI testing to assess the axon-mediated flare area in response to 10% acetylcholine iontophoresis. LDI measurements were taken before and longitudinally after a 48-hour application of 0.1% capsaicin (to cause a transient small fiber neuropathy) on the skin of the thigh; placebo cream was placed on the contralateral thigh as a control. We compared our new LDI image analysis technique to two previously published methods. The new LDI analysis technique was the only method to show a consistent difference in axon-reflex area between capsaicin treated and placebo treated skin on all testing days (p<0.05) with maximum attenuation of the flare area immediately post-application (438 ±298 mm2 vs. 824 ±375 mm2, p<0.05). In conclusion, this study demonstrates that our novel flare area method for LDI analysis can detect neurovascular dysfunction in a model of small fiber neuropathy, is an improvement over existing methods, and may supplement clinical assessment of small fiber neuropathy. PMID:23850386

Illigens, Ben M.W.; Siepmann, Timo; Roofeh, Joe; Gibbons, Christopher H.

2013-01-01

97

Laser doppler flowmetry evaluation as a pulpal vitality test; Avaliacao da fluxometria laser doppler como teste de vitalidade pulpar  

Energy Technology Data Exchange (ETDEWEB)

The more frequently used pulp vitality tests (PVTs) are the thermal (cold and heat) and the electrical stimulus. These tests are, however, subjective, depending on the sensitivity threshold of each individual, and usually fail when immature or recently traumatised teeth are tested. The laser Doppler flowmetry (LDF) have been suggested as a PVT, by evaluating the pulp measured flow (F). The measured quantity F, used to discriminate healthy and non-vital teeth, is sensitive to factors hardly controlled or predictable, such as the LDFs and probe response differences, and the flow variations among individuals. It was suggested recently a new discriminator, F(%), less sensitive to such factors. The PVTs performances for F (%) and F as discriminators, however, were not known. The present study aimed to evaluate the PVTs' performances using the quantities F(%) and F (dif) as discriminators, both derived from F, and to compare, qualitatively and quantitatively, their performances to that obtained by using F. The quantities F(%) and F(dif) are, respectively, the ratio and the difference of the flow from the interrogated tooth and its healthy homologous, being F(dif) a proposed new discriminator. The obtained confidence intervals (95% of significance) of the areas under ROC curves were from 0,964 to 1,000 for F (%); from 0,959 to 1,000 for F (dif) and; from 0,584 to 0,951 for F; showing that F(%) and F (dif) are more reliable discriminators then F. (author)

Eduardo, Flavia Tavares de Oliveira de Paula

2004-07-01

98

Infrared Doppler laser systems for the remote measurement of winds  

Energy Technology Data Exchange (ETDEWEB)

Theoretical principles are presented for the Doppler lidar measurement of wind velocity. A method for measuring the structural constant of wind velocity fields is proposed. A scheme of a continuous monostatic Doppler lidar is described, and results of full-scale and comparative measurements of wind velocity profiles and structural constant are reported. 10 refs.

Akhmanov, S.A.; Gordienko, V.M.; Kosovskii, L.A.; Kurochkin, N.N.; Pogosov, G.A. (Moskovskii Gosudarstvennyi Universitet, Moscow (USSR))

1991-02-01

99

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

100

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

 
 
 
 
101

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

102

Optical microcirculatory skin model: Assessed by Monte Carlo simulations paired with in vivo laser Doppler flowmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An optical microvascular skin model, valid at 780 nm, was developed. The model consisted of six layers with individual optical properties, and variable thicknesses and blood concentrations at three different blood flow velocities. Monte Carlo simulations were used to evaluate the impact of various model parameters on the traditional Laser Doppler flowmetry (LDF) measures. A set of reference Doppler power spectra was generated by simulating 7,000 configurations, varying the thickness and blood...

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

2008-01-01

103

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

104

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

105

Atmospheric transmission of CO2 laser radiation with application to laser Doppler systems  

Science.gov (United States)

The molecular absorption coefficients of carbon dioxide, water vapor, and nitrous oxide are calculated at the P16, P18, P20, P22, and P24 lines of the CO2 laser for temperatures from 200 to 300 K and for pressures from 100 to 1100 mb. The temperature variation of the continuum absorption coefficient of water vapor is taken into account semi-empirically from Burch's data. The total absorption coefficient from the present calculations falls within + or - 20 percent of the results of McClatchey and Selby. The transmission loss which the CO2 pulsed laser Doppler system experiences was calculated for flight test conditions for the five P-lines. The total transmission loss is approximately 7 percent higher at the P16 line and 10 percent lower at the P24 line compared to the P20 line. Comparison of the CO2 laser with HF and DF laser transmission reveals the P2(8) line at 3.8 micrometers of the DF laser is much better from the transmission point of view for altitudes below 10 km.

Murty, S. S. R.

1975-01-01

106

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

107

Full-Field Laser-Doppler Imaging and Its Physiological Significance for Tissue Blood Perfusion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using Monte Carlo simulations for a semi-infinite medium representing a skeletal muscle tissue, it is demonstrated that the zero- and first-order moments of the power spectrum for a representative pixel of a full-field laser-Doppler imager behave differently from classical laser-Doppler flowmetry. In particular, the zero-order moment has a very low sensitivity to tissue blood volume changes, and it becomes completely insensitive if the probability for a photon to interact with a moving red bl...

Binzoni, T.; Ville, D.

2008-01-01

108

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

CERN Document Server

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

109

Laser backscattering analytical model of Doppler power spectra about rotating convex quadric bodies of revolution  

Science.gov (United States)

We propose an analytical model of Doppler power spectra in backscatter from arbitrary rough convex quadric bodies of revolution (whose lateral surface is a quadric) rotating around axes. In the global Cartesian coordinate system, the analytical model deduced is suitable for general convex quadric body of revolution. Based on this analytical model, the Doppler power spectra of cones, cylinders, paraboloids of revolution, and sphere-cones combination are proposed. We analyze numerically the influence of geometric parameters, aspect angle, wavelength and reflectance of rough surface of the objects on the broadened spectra because of the Doppler effect. This analytical solution may contribute to laser Doppler velocimetry, and remote sensing of ballistic missile that spin.

Gong, YanJun; Wu, ZhenSen; Wang, MingJun; Cao, YunHua

2010-01-01

110

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)

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)

112

Laser Doppler, velocimeter system for turbine stator cascade studies and analysis of statistical biasing errors  

Science.gov (United States)

A laser Doppler velocimeter (LDV) built for use in the Lewis Research Center's turbine stator cascade facilities is described. The signal processing and self contained data processing are based on a computing counter. A procedure is given for mode matching the laser to the probe volume. An analysis is presented of biasing errors that were observed in turbulent flow when the mean flow was not normal to the fringes.

Seasholtz, R. G.

1977-01-01

113

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

114

The flaws of laser Doppler in negative-pressure wound therapy research.  

Science.gov (United States)

Recent studies, using modalities other than laser Doppler, have indicated that perfusion during negative-pressure wound therapy (NPWT) is reduced, contrary to world literature. The aim of the present study was to evaluate whether the measuring technique of the laser Doppler could be influenced by the compressive nature of NPWT dressings and whether this could explain the conflicting findings. A hypothesis that it may be possible for laser Doppler to record similar readings to those obtained during NPWT by merely compressing tissues manually was tested on 12 NPWT dressings, with each undergoing an alternating series of manual compressive forces and NPWT (-125?mmHg). During the periods of NPWT (n?=?12), the mean perfusion recording increased in five experiments, reduced in six, and remained unchanged in one. During the period when manual pressure was applied (n?=?12), there was a mean increase in perfusion in six experiments and a reduction in six. The type of change in perfusion (increase or decrease) was the same for both NPWT and manual pressure in 10 of the 12 experiments. In conclusion, laser Doppler can incorrectly record increased perfusion when tissues are compressed, implying that it is flawed in the field of NPWT research as tissues are always compressed to some degree by the NPWT dressing. PMID:24844341

Kairinos, Nicolas; McKune, Andrew; Solomons, Michael; Hudson, Donald A; Kahn, Delawir

2014-01-01

115

Doppler-free laser-induced fluorescence of oxygen atoms in a flame  

International Nuclear Information System (INIS)

Two-photon absorption of laser radiation can be used to excite atoms to high lying electronic levels having the same parity as that of the ground electronic state. This permits the laser detection of species whose one-photon transitions lie too far in the vacuum ultraviolet to be accessible in normal laboratory and combustion environments. Such two-photon laser-induced fluorescence in oxygen atoms was first studied in a flow discharge cell and was later used for flame detection. This paper discusses an appropriate geometric arrangement of counterpropagating laser beams, which enables two-photon absorption to be carried out in such a way that the resulting transition does not exhibit Doppler broadening. The Doppler width, caused by the motion of the absorbing atoms, is similar in magnitude to collisional linewidths under conditions of atmospheric pressure and flame temperatures. In Doppler-free spectroscopy, the linewidth is caused only by that natural or lifetime broadening, either radiative or collisional. Such collisions include energy transfer and quenching as well as collisions which interrupt the phase of the absorbed radiation. A measure of the linewidth under Doppler-free conditions thus furnishes an upper limit to the rate of quenching of the radiating, electronically excited state

116

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

International Nuclear Information System (INIS)

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

117

Comparison of temporal response to cerebral blood flow measured by laser speckle flowgraphy and laser Doppler flowmetry  

Science.gov (United States)

Cerebral blood flow (CBF) change of mice during whisker stimulation is measured by laser speckle flowgraphy (LSFG) and laser Doppler flowmetry (LDF). Laser speckle flowgraphy (LSFG) has been used to obtain the two-dimensional distribution of the blood flow in tissue as well as scanning laser Doppler flowmetry (LDF). There are several parameters of LSFG to obtain the blood flow maps and the distribution change of blood flow. In this study, we calculate four parameters from the speckle pattern to measure CBF in awake mice. The temporal resolution of LSFG is likely to be less than that of LDF. The temporal changes in CBF obtained from the four parameters calculated from the speckle pattern detected by a common CCD camera are compared with those measured by LDF. The time courses of CBF change measured by LSFG highly correlate with those by LDF. The results indicate that the temporal response of LSFG is sufficient to measure CBF change evoked by brain activations.

Kusano, Masashi; Nakayama, Haruka; Takuwa, Hiroyuki; Masamoto, Kazuto; Kanno, Iwao; Okada, Eiji

2011-07-01

118

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

DEFF Research Database (Denmark)

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

Rodrigo, Peter John; Pedersen, Christian

2009-01-01

119

Three-dimensional laser cooling at the Doppler limit  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many predictions of Doppler cooling theory of two-level atoms have never been verified in a three-dimensional geometry, including the celebrated minimum achievable temperature $\\hbar \\Gamma/2 k_B$, where $\\Gamma$ is the transition linewidth. Here, we show that, despite their degenerate level structure, we can use Helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the s...

Chang, Rockson; Hoendervanger, Lynn; Bouton, Quentin; Fang, Yami; Klafka, Tobias; Audo, Kevin; Aspect, Alain; Westbrook, Christoph I.; Cle?ment, David

2014-01-01

120

Laser Doppler microscopy of blood flows in fish embryos at different stages of ontogenesis  

Science.gov (United States)

Laser Doppler microscopy is an efficient method of in vivo measurements of flow velocities in different biological objects. It is based on the registration of frequency shifts in light quasielastically scattered from particles moving in the flows. To study the embryonic development of the cardiac-vascular system in embryos of warm water fishes, embryos of Macropodus opercularis have been used. Doppler spectra from pulsatile blood flows in selected vessels and their changes in the process of ontogenesis have been registered. The recording of the successive spectra and their computer processing yield the varying dynamics of blood flows. Typical age dependencies of velocity patterns in the embryos are presented.

Savchenko, Natalia B.; Priezzhev, Alexander V.; Levenko, Borislav A.

1995-02-01

 
 
 
 
121

Differential Laser Doppler based Non-Contact Sensor for Dimensional Inspection with Error Propagation Evaluation  

Directory of Open Access Journals (Sweden)

Full Text Available To achieve dynamic error compensation in CNC machine tools, a non-contactlaser probe capable of dimensional measurement of a workpiece while it is being machinedhas been developed and presented in this paper. The measurements are automatically fedback to the machine controller for intelligent error compensations. Based on a well resolvedlaser Doppler technique and real time data acquisition, the probe delivers a very promisingdimensional accuracy at few microns over a range of 100 mm. The developed opticalmeasuring apparatus employs a differential laser Doppler arrangement allowing acquisitionof information from the workpiece surface. In addition, the measurements are traceable tostandards of frequency allowing higher precision.

Ketsaya Vacharanukul

2006-06-01

122

Dual beam translator for use in laser doppler anemometry  

Energy Technology Data Exchange (ETDEWEB)

A method is described for attaining substantial spacial coincidence of the intersection volumes of two pairs of intersecting light beams in a fluid flow conduit in a Doppler anemometry device. The method comprises focusing the two pairs of light beams with a beam focusing means and selectively translating the beam paths of at least one of the pairs of beams. The paths are translated in a direction parallel to the original beam paths by a pair of rotatable transparent optical means provided in the beam paths between the beam focusing means and the fluid flow conduit.

Brudnoy, D.M.

1987-01-20

123

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

Science.gov (United States)

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

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

2014-01-01

124

Experimental comparison of perfusion imaging systems using multi-exposure laser speckle, single-exposure laser speckle, and full-field laser Doppler  

Science.gov (United States)

A variety of laser Doppler and laser speckle contrast systems have been constructed by various groups and companies, for commercial sale and for research. All rely on the same physical phenomenon - the dynamic laser speckle pattern generated by illuminating tissue with coherent light - but differ in details of system design, operation and analysis. We present a comparison between measurements made with three systems: a multi-exposure laser speckle contrast system built at Industrial Research Ltd, a commercial single-exposure laser speckle contrast system developed by Perimed AB (PSI NR) and the full-field laser Doppler camera built by the University of Twente (TOPCam). We compare the response to changing flows of all three systems. The systems are found to produce similar results for a variety of in-vivo and in-vitro measurements. Multi-exposure speckle contrast shows some advantages in information gained and insensitivity to static speckle, at the cost of increased complexity and measurement time.

Thompson, Oliver; Bakker, Jimmy; Kloeze, Carla; Hondebrink, Erwin; Steenbergen, Wiendelt

2012-03-01

125

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

Scientific Electronic Library Online (English)

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

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

2004-12-01

126

Measurement of the Doppler power of flowing blood using ultrasound Doppler devices.  

Science.gov (United States)

Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser-receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and echogenicity of flowing blood were compared with those obtained in several previous studies. PMID:25542489

Huang, Chih-Chung; Chou, Hung-Lung; Chen, Pay-Yu

2015-02-01

127

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

Science.gov (United States)

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

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

2011-02-01

128

Changes of microvascular perfusion of lower leg musculature after percutaneous transluminal angioplasty (PTA), evaluated by intramuscular laser doppler fluxmetry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background Prior studies have shown significant changes in the bloodflow of the big leg-vessels and resistance vessels after a percutaneous transluminal angioplasty (PTA) . For this study the intramuscular single-fibre laser-doppler-flowmetry (im-SFLDF) was examined for a potential advantages of this method compared to non-invasive methods such as transcutaneous laser-doppler-flowmetry, transcutaneous oxygen partial pressure measurement (tcPO2), venous occlusion plethysmography (VVP) and ...

Lotz, Christian

2013-01-01

129

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

International Nuclear Information System (INIS)

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. This is the normal situation, e.g., in magneto-optical traps (MOT). The Doppler limit heating rate due to radiative collisions is calculated for 24Mg atoms in an MOT based on the 1S0-1P1 atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We also describe a channeling 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

130

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

131

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

132

Determination of relationship between Rayleigh wave velocity and stress with laser Doppler velocimeter  

Science.gov (United States)

A non-contact measurement technique of Rayleigh wave velocity is proposed. In the non-contact measurement system, a laser Doppler velocimeter is used to determine wave motions. With above technique, the relationship between Rayleigh wave velocity and stress for an aluminum alloy 5052 and steel SS400 is determined, and the results are in good agreement with that obtained by contact measurement method.

He, Lingfeng; Kobayashi, Shoichi

2002-05-01

133

Twente Optical Perfusion Camera: system overview and performance for video rate laser Doppler perfusion imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the Twente Optical Perfusion Camera (TOPCam), a novel laser Doppler Perfusion Imager based on CMOS technology. The tissue under investigation is illuminated and the resulting dynamic speckle pattern is recorded with a high speed CMOS camera. Based on an overall analysis of the signal-to-noise ratio of CMOS cameras, we have selected the camera which best fits our requirements. We applied a pixel-by-pixel noise correction to minimize the influence of noise in the perfusion images. We...

Draijer, M.; Hondebrink, E.; Leeuwen, T.; Steenbergen, W.

2009-01-01

134

Monitoring blood flow to colorectal liver metastases using laser Doppler flowmetry: the effect of angiotensin II.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many colorectal liver metastases are hypovascular, and their low level of perfusion is associated with limited drug uptake and poor response rates with regional chemotherapy. We have previously shown that hepatic arterial vasoconstrictors may increase drug delivery to liver tumours, but the underlying haemodynamic changes have not been defined. Using intraoperative laser Doppler flowmetry (LDF) we have assessed the effect of intraarterial angiotensin II (AI) on tumour blood flow in ten patien...

Hemingway, D. M.; Angerson, W. J.; Anderson, J. H.; Goldberg, J. A.; Mcardle, C. S.; Cooke, T. G.

1992-01-01

135

The effect of prazosin on skin microcirculation as assessed by laser Doppler flowmetry.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

1. Laser Doppler flowmetry was used in six normal volunteers to record changes in fingertip skin blood flow after the administration of prazosin to block postsynaptic alpha 1-adrenoceptors. 2. Prazosin (0.5 mg orally) did not alter systolic or diastolic blood pressure or heart rate. 3. Prazosin did significantly increase basal skin blood flow 2 h after its administration but this effect was no longer evident after contralateral hand warming. Prazosin markedly reduced the skin vasoconstrictor ...

Khan, F.; Struthers, A. D.; Spence, V. A.

1988-01-01

136

Evaluation of phasic blood flow velocity in the great cardiac vein by a laser Doppler method.  

Science.gov (United States)

In the present study, characteristics of the phasic flow pattern in the great cardiac vein and the mechanism of such pattern formation were investigated using a laser Doppler velocimeter with an optic fiber probe. The laser Doppler velocimeter allowed measurements of venous blood velocity under more physiological conditions than were possible with previous methods. Moreover, venous blood flow measurement in the great cardiac vein mirrors the effects of myocardial contraction on the venous flow more directly than does measurement in the coronary sinus. Thus, our method is considered very useful. Results obtained from the present study are as follows: 1) Measurement of the phasic flow in the great cardiac vein was made in 11 anesthetized dogs using our laser Doppler method. The blood velocity curve obtained in the great cardiac vein was always characterized by a prominent systolic flow wave (SFW). The mean value for the maximum velocities under control conditions in 11 cases was 40 +/- 13 cm/s. The blood velocity increased with the onset of left ventricular ejection and decreased gradually after the peak formation at mid- or late systole.--2) Besides the above SFW, one or two small wave components were frequently observed during the atrial contraction period and/or during the isovolumic contraction phase. On the waveform during the atrial contraction period, two cases showed forward flow, while one case showed reverse flow. The small reverse flow waves during the isovolumic contraction phase were found in seven cases.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2936713

Kajiya, F; Tsujioka, K; Goto, M; Wada, Y; Tadaoka, S; Nakai, M; Hiramatsu, O; Ogasawara, Y; Mito, K; Hoki, N

1985-02-01

137

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

CERN Document Server

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

138

Frequency stabilization of the 1064-nm Nd:YAG lasers to Doppler-broadened lines of iodine  

Science.gov (United States)

In this study a diode-laser pumped Nd:YAG laser is frequency stabilized by locking its frequency-doubled output to the center of unsaturated (Doppler-broadened) transitions if the (127)I2 molecule. In this process the successive two-sample deviation of the laser frequency (root Allan variance) is kept below 5.67 kHz, or 2 parts in 10(exp 11) of the laser frequency, for averaging times between 10 ms and 40 s. Results of this study show that this locking technique is simpler and requires less power than locking to Doppler-free lines.

Arie, Ady; Byer, Robert L.

1993-12-01

139

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

A compact master-oscillator power-amplifier semiconductor laser (MOPA-SL) is a good candidate for a coherent light source (operating at 1550 nm) in a Doppler wind Lidar. The MOPA-SL requires two injection currents: Idfb for the distributed-feedback (DFB) laser section (master oscillator) and Iamp for the tapered amplifier section. The specified maximum current values are 0.7 A and 4.0 A for Idfb and Iamp. Although the MOPA-SL has been proven capable of producing single-frequency CW output bea...

Rodrigo, Peter John; Pedersen, Christian

2009-01-01

140

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

DEFF Research Database (Denmark)

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

Rodrigo, Peter John; Pedersen, Christian

2012-01-01

 
 
 
 
141

Ultrasonic detection of photothermal interaction of lasers with tissue using a pulsed Doppler system  

Science.gov (United States)

Thermal therapy using various heating sources such as lasers or microwaves to destroy benign and malignant lesions has recently gained widespread acceptance. However, the accurate prediction of thermal damage in tissue according to theoretical or computer modeling is difficult and unreliable due to target variability with respect to physical properties, geometry, and blood perfusion. Thus, one of the major obstacles to application of thermal therapies has been the lack of a noninvasive, real-time method that could determine the extent and geometry of treated tissue. To evaluate the effects of laser heating on tissue, we have developed an analog-digital hybrid Doppler ultrasound system to measure the phase and amplitude of ultrasonic echoes returned from the heated tissue. The system consists of an eight-gate pulsed Doppler detector, a 16-channel 12-bit A/D converter, and a signal analysis and visualization software package. In vitro studies using canine liver showed two distinct types of modulation of the echoes along the ultrasound beam path during laser irradiation using an 810 nm diode laser. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 2 signals showed large and rapid variations in amplitude and phase which usually appeared after tissue surface explosion and were indicative of tissue ablation. We hypothesize that the observed phase changes in type 1 signals are due to thermal effects within the tissue consistent with tissue expansion and contraction while the phase changes in type 2 signals are likely due to formation and motion of gas bubbles in the tissue. A further development of the Doppler ultrasound technique could lead to the generation of feedback information needed for monitoring and automatic control of thermal treatment using various heating modalities such as laser, high intensity focused ultrasound, microwaves, or radio frequency waves.

Ying, Hao; Azeemi, Aamer; Hartley, Craig J.; Motamedi, Massoud; Bell, Brent A.; Rastegar, Sohi; Sheppard, L. C.

1995-05-01

142

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

Science.gov (United States)

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

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

2014-05-01

143

Absolute and dynamic position and shape measurement of fast moving objects employing novel laser Doppler techniques  

Science.gov (United States)

In this contribution a novel laser Doppler distance (LDD) sensor is presented, which allows simultaneous measurement of axial position and tangential velocity and, thus, determination of the shape of moving and especially rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-shaped interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It will be shown that, in contrast to conventional distance sensors, high temporal resolution below 3 ?s and high position resolution of about 1 ?m can be achieved simultaneously, because the position uncertainty of the LDD sensor is in principle independent of the object velocity. This is advantageous especially for monitoring highly dynamic processes e.g. at turbo machines, where in-process measurements of tip clearance and rotor vibrations are reported for up to 600 m/s blade tip velocity.

Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

2008-09-01

144

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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, sei...

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

2004-01-01

145

A novel laser doppler linear encoder using multiple-reflection optical design for high-resolution linear actuator.  

Energy Technology Data Exchange (ETDEWEB)

A novel laser Doppler linear encoder system (LDLE) has been developed at the Advanced Photon Source, Argonne National Laboratory. A self-aligning 3-D multiple-reflection optical design was used for the laser Doppler displacement meter (LDDM) to extend the encoder system resolution. The encoder is compact [about 70 mm(H) x 100 mm(W) x 250 mm(L)] and it has sub-Angstrom resolution, 100 mm/sec measuring speed, and 300 mm measuring range. Because the new device affords higher resolution, as compared with commercial laser interferometer systems, and yet cost less, it will have good potential for use in scientific and industrial applications.

Shu, D.

1998-07-16

146

Nonlinear ultrasonic image of fatigue cracks by using laser doppler vibrometry  

Energy Technology Data Exchange (ETDEWEB)

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

Cheong, Yong Moo; Kim, Ha Nam; Lee, Duck Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-10-15

147

Performance analysis of continuous tracking laser Doppler vibrometry applied to rotating structures in coast-down  

International Nuclear Information System (INIS)

In this paper a performance analysis of the so-called tracking continuous scanning laser Doppler vibrometry (TCSLDV) exploited in coast-down has been performed. This non-contact measurement system is able to scan continuously over a rotating surface during coast-down and to determine vibration operational deflection shapes (ODSs) and natural frequencies in short time, i.e. the temporal extent of the coast-down. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the whole rotor surface synchronously with its rotation, so that the LDV output is modulated by the structure's ODSs. This technique has a full-field nature that enables it to measure simultaneously the time and spatial dependence of the vibration in a unique measurement. However, the TCSLDV presents some criticalities in practical applications, especially when applied to rotary transient and fast processes. In fact, if the vibration is transient and decays very fast, then the laser beam could not have had the time to scan the complete structure surface and the modulation of the ODS could be partial. An analytical model reproducing a representative experiment has been developed in order to evaluate the sensitivity of results to testing conditions. The laser beam trajectory in both the fixed and rotating reference systems has been synthesized showing its dependence on experimental parameters as the rotation speed variation during coast-down. It has been demonstrated the decrease in speed induces the deformation of the laser trajectory influencing the LDV output time history, spectrum and consequently the recovered ODS. (paper)

148

Performance analysis of continuous tracking laser Doppler vibrometry applied to rotating structures in coast-down  

Science.gov (United States)

In this paper a performance analysis of the so-called tracking continuous scanning laser Doppler vibrometry (TCSLDV) exploited in coast-down has been performed. This non-contact measurement system is able to scan continuously over a rotating surface during coast-down and to determine vibration operational deflection shapes (ODSs) and natural frequencies in short time, i.e. the temporal extent of the coast-down. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the whole rotor surface synchronously with its rotation, so that the LDV output is modulated by the structure's ODSs. This technique has a full-field nature that enables it to measure simultaneously the time and spatial dependence of the vibration in a unique measurement. However, the TCSLDV presents some criticalities in practical applications, especially when applied to rotary transient and fast processes. In fact, if the vibration is transient and decays very fast, then the laser beam could not have had the time to scan the complete structure surface and the modulation of the ODS could be partial. An analytical model reproducing a representative experiment has been developed in order to evaluate the sensitivity of results to testing conditions. The laser beam trajectory in both the fixed and rotating reference systems has been synthesized showing its dependence on experimental parameters as the rotation speed variation during coast-down. It has been demonstrated the decrease in speed induces the deformation of the laser trajectory influencing the LDV output time history, spectrum and consequently the recovered ODS.

Martarelli, M.; Castellini, P.

2012-06-01

149

Comparison of blood flow measurements by hydrogen gas clearance and laser Doppler flowmetry in the rat duodenum  

International Nuclear Information System (INIS)

This report examines the relationship between hydrogen gas clearance and laser Doppler flowmetry measurements in the duodenum of fasted, anesthetized rats under conditions of 1) reduced perfusion due to graded levels of hemorrhagic hypotension or 2) hyperemia due to perfusion with step doses of acid. There was a significant correlation between hydrogen gas clearance and laser Doppler flowmetry measurements. The change in laser Doppler flowmetry values from the period immediately before to the period during the 3 min. of acid perfusion was significantly correlated with the dose of acid used. The changes in hydrogen gas clearance and laser Doppler flowmetry values from the 30 min. period before to the 30 min. period after acid perfusion were not correlated with the dose of acid used. It is concluded that in the rat duodenum 1) the significant linear correlation between hydrogen gas clearance and laser Doppler flowmetry when blood flow is reduced suggests that the countercurrent exchange mechanism is unlikely to modulate significant hydrogen gas clearance measurements, and 2) the dose-related acid-induced duodenal hyperemia is transient rather than perisitent when the rat duodenum is exposed to hydrochlorid acid for 3 min. 25 refs

150

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

Directory of Open Access Journals (Sweden)

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

Afanasieva G.A.

2011-12-01

151

Monostatic coaxial 1.5 ?m laser Doppler velocimeter using a scanning Fabry-Perot interferometer.  

Science.gov (United States)

We present a laser Doppler velocimeter (LDV) in monostatic coaxial arrangement consisting of off-the-shelf telecom-grade components: a single frequency laser (wavelength ? = 1.5 ?m) and a high-finesse scanning Fabry-Perot interferometer (sFPI). In contrast to previous 1.5 ?m 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. PMID:24103985

Rodrigo, Peter John; Pedersen, Christian

2013-09-01

152

Progress report on LOFT transit time flowmeter  

International Nuclear Information System (INIS)

Experiments and preliminary theoretical results indicate that transit time flowmeters using thermocouples as sensors are not useful in Loss-of-Fluid Test (LOFT) blowdown experiments. Work is in progress to determine whether transit time flowmeters using other types of sensors might be useful in LOFT

153

Full-field laser-Doppler imaging and its physiological significance for tissue blood perfusion  

International Nuclear Information System (INIS)

Using Monte Carlo simulations for a semi-infinite medium representing a skeletal muscle tissue, it is demonstrated that the zero- and first-order moments of the power spectrum for a representative pixel of a full-field laser-Doppler imager behave differently from classical laser-Doppler flowmetry. In particular, the zero-order moment has a very low sensitivity to tissue blood volume changes, and it becomes completely insensitive if the probability for a photon to interact with a moving red blood cell is above 0.05. It is shown that the loss in sensitivity is due to the strong forward scatter of the propagating photons in biological tissues (i.e., anisotropy factor g = 0.9). The first-order moment is linearly related to the root mean square of the red blood cell velocity (the Brownian component), and there is also a positive relationship with tissue blood volume. The most common physiological interpretation of the first-order moment is as tissue blood volume times expectation of the blood velocity (in probabilistic terms). In this sense, the use of the first-order moment appears to be a reasonable approach for qualitative real-time blood flow monitoring, but it does not allow us to obtain information on blood velocity or volume independently. Finally, it is shown that the spatial and temporal resolution trade-off imposed by the CMOS detectors, used in full-field laser-Doppler hardware, may lead to measurements that vary oppositely with the underlying physiological quanely with the underlying physiological quantities. Further improvements on detectors' sampling rate will overcome this limitation.

154

Full-field laser-Doppler imaging and its physiological significance for tissue blood perfusion.  

Science.gov (United States)

Using Monte Carlo simulations for a semi-infinite medium representing a skeletal muscle tissue, it is demonstrated that the zero- and first-order moments of the power spectrum for a representative pixel of a full-field laser-Doppler imager behave differently from classical laser-Doppler flowmetry. In particular, the zero-order moment has a very low sensitivity to tissue blood volume changes, and it becomes completely insensitive if the probability for a photon to interact with a moving red blood cell is above 0.05. It is shown that the loss in sensitivity is due to the strong forward scatter of the propagating photons in biological tissues (i.e., anisotropy factor g = 0.9). The first-order moment is linearly related to the root mean square of the red blood cell velocity (the Brownian component), and there is also a positive relationship with tissue blood volume. The most common physiological interpretation of the first-order moment is as tissue blood volume times expectation of the blood velocity (in probabilistic terms). In this sense, the use of the first-order moment appears to be a reasonable approach for qualitative real-time blood flow monitoring, but it does not allow us to obtain information on blood velocity or volume independently. Finally, it is shown that the spatial and temporal resolution trade-off imposed by the CMOS detectors, used in full-field laser-Doppler hardware, may lead to measurements that vary oppositely with the underlying physiological quantities. Further improvements on detectors' sampling rate will overcome this limitation. PMID:18997268

Binzoni, T; Van De Ville, D

2008-12-01

155

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

156

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

Energy Technology Data Exchange (ETDEWEB)

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.

Amols, H.I.; Goffman, T.E.; Komaki, R.; Cox, J.D.

1988-11-01

157

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

158

Heterodyne Doppler velocity measurement of moving targets by mode-locked pulse laser.  

Science.gov (United States)

In this study, heterodyne detection is adopted to measure the velocity of a target simulated by a rapidly rotating plate by using a mode-locked pulse laser as the resource. The coherent beat frequency of the signal light reflected by target and local oscillation light occurred on the surface of the detector. Then the waveform of beat frequency was processed by filtering to obtain the Doppler frequency shift of the signal light induced by target. With this frequency shift, the velocity of target could be obtained by calculation. Results indicate that the measurement has a high precision. The error on average is within 0.4 m/s. PMID:22274421

Bai, Yan; Ren, Deming; Zhao, Weijiang; Qu, Yanchen; Qian, Liming; Chen, Zhenlei

2012-01-16

159

Investigations of fast-rotating bodies using an interferometric laser Doppler distance sensor system  

Science.gov (United States)

One challenge in micrometrology is to measure precisely the shape of fast moved objects with high temporal resolution. Deformation measurements of lightweight composite materials are of importance to guarantee its robustness e.g. against impacts. In a high-speed rotor test rig their elastic and plastic deformations due to centrifugal forces can be evaluated. Non-contact inspection techniques with micron resolution under vacuum conditions are necessary. For the first time, we present high-speed deformation measurements of a cylindrical rotor by a non-incremental laser Doppler distance sensor system using fiber and diffractive optics. Besides the determination of the radial enlargement also wobbling of the rotor was monitored.

Günther, P.; Dreier, F.; Pfister, T.; Czarske, J.; Haupt, T.; Gude, M.; Hufenbach, W.

2010-05-01

160

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

 
 
 
 
161

High resolution laser induced fluorescence Doppler velocimetry utilizing saturated absorption spectroscopy  

International Nuclear Information System (INIS)

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

162

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

163

Laser doppler flow imaging of open lower leg fractures in an animal experimental model.  

Directory of Open Access Journals (Sweden)

Full Text Available PURPOSE: Open lower leg fractures are frequently associated with severe soft tissue damage, followed by osteomyelitis. Using an animal experimental model, we investigated the effect of timing of coverage of a tibial fracture with a local muscle flap. METHODS: 80 rabbits had a tibial fracture induced in a standardised fashion, which was stabilised by screw osteosynthesis. After 3 (group A; n=40 and 7 days (group B; n=40, respectively, the tissue defect was covered by a local gastrocnemius flap. In increasing intervals from 1 to 2, 4, 8, and 16 weeks, the rabbits from each group were killed and the bone fracture was analysed histomorphologically. Cortical microcirculation was measured by 2-channel laser doppler flowmetry. RESULTS: Muscle flaps after 3 days improved perfusion significantly as compared with 7 days (24 Flux [standard error, 5 Flux] versus 10 Flux [3 Flux]; baseline, 1.4 Flux. Group A animals also displayed a lower rate of necrosis (0 versus 38. The incidence of osteomyelitis was higher in group B than in group A (24% versus 0%. CONCLUSION: Laser doppler flowmetry was proven to be a reliable, minimally invasive means for identifying avital tissue, leading to reduction in the loss of vital bone tissue in experimental settings.

Herzog L

2002-12-01

164

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.

165

Assessment of measurement efficiency in laser- and phase-Doppler techniques: an information theory approach  

International Nuclear Information System (INIS)

Laser- and phase-Doppler diagnostic techniques provide information on particle characteristics in the form of discrete probability distribution functions. Most methods assess the amount of information required for an accurate measurement through the first- and second-order moments of these distributions. However, considering that a measurement is the distribution and not its moments, a different approach is developed based on information theory (IT) concepts in order to assess if the information provided to the experimentalist is enough to ensure an accurate statistical analysis. The methodology and stopping criteria are presented and used in previously reported measurements obtained with laser- and phase-Doppler techniques. Results show that using an IT approach to assess the reliability of data provided by a measurement means evaluating the degree of stabilization of a discrete probability distribution, where more information acquired does not necessarily imply a more accurate measurement. The statistical analysis performed using the number of samples indicated by the IT method, compared to the total sample size previously measured, shows similar results. Moreover, measurement time is substantially reduced if the IT method is used, thus improving measurement efficiency. (paper)

166

Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry  

Science.gov (United States)

We developed a micro multipoint laser Doppler velocimeter (?-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the ?-MLDV. Although average velocity is generally estimated from a peak position ( f peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.

Ishida, Hiroki; Yasue, Youichi; Hachiga, Tadashi; Andoh, Tsugunobu; Akiguchi, Shunsuke; Kuraishi, Yasushi; Shimizu, Tadamichi

2014-07-01

167

Determination of Stress-Acoustic Coefficients of Rayleigh Wave by Use of Laser Doppler Velocimetry  

Science.gov (United States)

In the present paper, 1) a new non-contact ultrasonic stress measurement technique is proposed based on acoustoelasticity, in which ultrasonic wave motion is detected by use of a laser Doppler velocimeter, and 2) the stress-acoustic coefficients of Rayleigh wave for aluminum alloy and structural steel are determined by the technique. In the measurement system, Rayleigh waves are emitted into the specimen by a wedge-type piezoelectric transducer and vertical velocities of the surface motions of the traveling Rayleigh waves are detected by the laser Doppler velocimeter at two points of 4 cm apart. In order to measure the traveling time of the wave between the two points, the converted voltage signals are supplied both to i) a sing-around unit and ii) to a digital oscilloscope. The time-of-flight over the distance between the two points is obtained either by subtracting the sing-around periods measured at the two points or by direct reading at zero-cross of the overlapped images of the two waves on the CR display of the oscilloscope. Both measurements are made at the same time under increasing or decreasing loads. The stress-acoustic coefficients obtained are -1.2×10-5/MPa and -0.21×10-5/MPa for aluminum alloy 5052 and structural steel SS400, respectively. These results are in good agreement with those determined using two knife-edge contact piezoelectric transducers. This study shows that the proposed non-contact measuring technique by use of laser velocimetry is applicable to determining the stress-acoustic coefficients.

He, Lingfeng; Kobayashi, Shoichi

168

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

169

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 techniqueut, 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)

170

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

International Nuclear Information System (INIS)

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

171

Development of the immersed sodium flowmeter  

International Nuclear Information System (INIS)

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

172

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

173

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

International Nuclear Information System (INIS)

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

174

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

Science.gov (United States)

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

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

2008-07-20

175

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

176

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

177

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

Science.gov (United States)

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

Mondal, S.; Lad, Amit D.; Ahmed, Saima; Narayanan, V.; Pasley, J.; Rajeev, P. P.; Robinson, A. P. L.; Kumar, G. Ravindra

2010-09-01

178

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

International Nuclear Information System (INIS)

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

179

Ultrasonic characterization of materials by means of under water Laser Doppler Vibrometer measurements of continuous waves  

Science.gov (United States)

Pulse signals are widely use for several ultrasonic testing. They indeed allow an easy estimation of the delays occurring in echo and transmission measurements and give the possibility to filter the noise (i.e undesired reflections occurring in the surface of the transducers) applying a window in the time domain. However their high crest factor makes these signals unsuitable to test attenuating materials. For this reason this paper proposes a new method, based on continuous waves, for ultrasonic characterization of materials. A a wave propagation model in the frequency domain is presented, to determine simultaneously acoustic velocity, mass density, and thickness of two Plexiglas plates, during transmission experiments. The Ultrasonic waves are captured by a Scanning Laser Doppler Vibrometer (SLDV) in order to guarantee a large number of spatial points, acquired with a high resolution.

Longo, Roberto; Steenackers, Gunther; Vanlanduit, Steve; Guillaume, Patrick

2010-05-01

180

Development of a scanning head for laser Doppler vibrometry (LDV) using dual optical wedges.  

Science.gov (United States)

A new laser Doppler vibrometry scanning head is proposed based on a pair of rotating optical wedges. A comprehensive mathematical model is developed and used to demonstrate how the wedges can be configured to scan point-by-point, in a line, in a circle, and in a combination of the two such that a straight line scan could be performed on a structure during rotation. Inevitable misalignments are incorporated into the model and considered quantitatively for the circular tracking application. Certain advantages are apparent over systems based on dual mirrors and a Dove prism in terms of lower apparent velocities at low rotation orders. A scanning head design for the circular tracking application is presented, together with experimental data showing good agreement between predicted and measured apparent velocities caused by misalignments. PMID:24387409

Rothberg, S J; Tirabassi, M

2013-12-01

 
 
 
 
181

Innovative technique for field calibration and inspection of large district heating meters. Laser doppler velocimetry (LDV)  

Energy Technology Data Exchange (ETDEWEB)

During the last three years, the Danish Technological Institute has managed and co-ordinated a recently completed R and D project aimed at developing an innovative method for field calibration and inspection of large district heating meters. The method is based on Laser Doppler Velocimetry (LDV) and the project has been carried out in close co-operation with partners from Danish district heating plants and supply companies, flow meter manufacturers, a leading manufacturer of LDV equipment and the Technical University of Denmark. The resulting measurement method has been developed with special reference to large (>200 mm diameter) district heating meters used for surveillance, control and billing, but the technique can also be used advantageously for flow measurements in almost any closed pipe system transporting transparent gases and liquids. Results of the project have been very satisfactory and the Danish Technological Institute expects to be able to offer fully accredited in-situ LDV measurements in the near future. (orig.)

Adams, M.; Frederiksen, J.; Drysdale, A. [Danish Technological Inst., Aarhus (Denmark); Hessel, C.E. [Aalborg Municipal Works (Denmark)

2002-10-01

182

Correlation between percutaneous penetration of methyl nicotinate and sensitive skin, using laser Doppler imaging.  

Science.gov (United States)

Cutaneous penetration of methyl nicotinate has been investigated in 20 women divided into reactors and non-reactors on the basis of response to 10% aqueous solution of lactic acid. The vasodilation induced was measured using a laser Doppler perfusion imager (LDPI) every 5 min for 1 h after application of methyl nicotinate. The intensity and duration of inflammation generated by methyl nicotinate were used to assess penetration of this chemical in persons with sensitive skin compared to those with normal skin. Significant differences were found between reactors and non-reactors. Reactors showed a significantly increased intensity of response to methyl nicotinate as early as 5 min after application, and for 30 min afterwards, though the duration of inflammation in these 2 groups was the same. Correlation between increased penetration of methyl nicotinate and skin response to lactic acid may suggest increased penetration of water-soluble chemicals in individuals with sensitive skin. PMID:9817223

Issachar, N; Gall, Y; Borrel, M T; Poelman, M C

1998-10-01

183

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

184

A microcomputer based frequency-domain processor for laser Doppler anemometry  

Science.gov (United States)

A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors.

Horne, W. Clifton; Adair, Desmond

1988-01-01

185

Perfusion assessment in rat spinal cord tissue using photoplethysmography and laser Doppler flux measurements  

Science.gov (United States)

Animal models are widely used to investigate the pathological mechanisms of spinal cord injury (SCI), most commonly in rats. It is well known that compromised blood flow caused by mechanical disruption of the vasculature can produce irreversible damage and cell death in hypoperfused tissue regions and spinal cord tissue is particularly susceptible to such damage. A fiberoptic photoplethysmography (PPG) probe and instrumentation system were used to investigate the practical considerations of making measurements from rat spinal cord and to assess its suitability for use in SCI models. Experiments to assess the regional perfusion of exposed spinal cord in anesthetized adult rats using both PPG and laser Doppler flowmetry (LDF) were performed. It was found that signals could be obtained reliably from all subjects, although considerable intersite and intersubject variability was seen in the PPG signal amplitude compared to LDF. We present results from 30 measurements in five subjects, the two methods are compared, and practical application to SCI animal models is discussed.

Phillips, Justin P.; Cibert-Goton, Vincent; Langford, Richard M.; Shortland, Peter J.

2013-03-01

186

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

CERN Document Server

In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a three dimensional laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working fluid, or limiting the fuel injection pressure. The vibrometer, which uses the Doppler effect to measure the velocity of a vibrating object, was used to scan injector nozzle tips during the injection event. The data were processed using a discrete Fourier transform to provide time-resolved spectra for valve-closed-orifice, minisac and microsac nozzle geometries, and injection pressures ranging from 60 to 160MPa, hence offering unprecedented insight into cyclic cavitation and internal mechanical dynamic processes. A peak was consistently f...

Crua, Cyril

2015-01-01

187

Accurate and precise calibration of AFM cantilever spring constants using laser Doppler vibrometry  

International Nuclear Information System (INIS)

Accurate cantilever spring constants are important in atomic force microscopy both in control of sensitive imaging and to provide correct nanomechanical property measurements. Conventional atomic force microscope (AFM) spring constant calibration techniques are usually performed in an AFM. They rely on significant handling and often require touching the cantilever probe tip to a surface to calibrate the optical lever sensitivity of the configuration. This can damage the tip. The thermal calibration technique developed for laser Doppler vibrometry (LDV) can be used to calibrate cantilevers without handling or touching the tip to a surface. Both flexural and torsional spring constants can be measured. Using both Euler–Bernoulli modeling and an SI traceable electrostatic force balance technique as a comparison we demonstrate that the LDV thermal technique is capable of providing rapid calibrations with a combination of ease, accuracy and precision beyond anything previously available. (paper)

188

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

189

Doppler cooling with coherent trains of laser pulses and tunable "velocity comb"  

CERN Document Server

We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, non-overlapping laser pulses. We develop an analytical model for treating the dynamic of a two-level system interacting with the resulting frequency comb field by using delta-function pulses. Supporting numerical calculations were carried out to verify the predictions of the model. We find that the radiative force mimics the underlying frequency comb structure. The force pattern depends strongly on the ratio of atomic lifetime to the repetition time and also on pulse area. For example, in the limit of short lifetimes or $\\pi$-pulses the frequency peaks of the radiative force wash out. We derive analytical expressions for the radiative force and for optimal parameters of the pulse train and study compression of velocity distribution.

Ilinova, Ekaterina; Derevianko, Andrei

2011-01-01

190

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, Århus 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: Ændringer 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

191

Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets  

Science.gov (United States)

Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the "noise" from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.

Cahoy, Kerri; Fischer, Debra; Spronck, Julien; DeMille, David

2010-07-01

192

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

193

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

194

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

195

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

International Nuclear Information System (INIS)

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 ?? = 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, ?-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.)

196

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

197

Laser Doppler field sensor for high resolution flow velocity imaging without camera  

International Nuclear Information System (INIS)

In this paper we present a laser sensor for highly spatially resolved flow imaging without using a camera. The sensor is an extension of the principle of laser Doppler anemometry (LDA). Instead of a parallel fringe system, diverging and converging fringes are employed. This method facilitates the determination of the tracer particle position within the measurement volume and leads to an increased spatial and velocity resolution compared to conventional LDA. Using a total number of four fringe systems the flow is resolved in two spatial dimensions and the orthogonal velocity component. Since no camera is used, the resolution of the sensor is not influenced by pixel size effects. A spatial resolution of 4 ?m in the x direction and 16 ?m in the y direction and a relative velocity resolution of 1x10-3 have been demonstrated up to now. As a first application we present the velocity measurement of an injection nozzle flow. The sensor is also highly suitable for applications in nano- and microfluidics, e.g., for the measurement of flow rates

198

A long pulse, high energy, narrow bandwidth carbon dioxide laser for doppler wind LIDAR applications  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the development of a carbon dioxide laser source with high energy (approx. 10 J/pulse), long pulses (approx. 2 microseconds), narrow bandwidth (approx. 200 kHz), and with a suitable discharge device (Lumonics 602) and cavity configuration (modified Self Filtering Unstable Resonator). An assessment is made of the feasibility of the high energy laser for long range, ground and satellite based, wind velocity measurements. The spectral behaviour is near to satisfying Doppler wind LIDAR requirements, the only problem being the fraction of pulse energy contained in the pulse peak, which is dispersed over a broad frequency spectrum. This can be a problem when looking at a very high velocity resolution and very long range measurements. A frequency bandwidth reduction is expected, at the expense of some output energy reduction, by working at sub-atmosphere pressure and with a nitrogen enriched gas mixture, in order to enhance the tail/spike amplitude ratio and thus to reduce the spike-related spectral broadening.

Barbini, R.; Belli, P.L.; Bitelli, G.; D' Amato, F.; Giorgi, M.; Galletti, E.; Stucchi, E.; Ferrario, A.

1990-05-01

199

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

200

Does tropicamide affect choroidal blood flow in humans? a laser Doppler flowmetry study  

Science.gov (United States)

The measurement of blood flow in the ocular fundus is of scientific and clinical interest. Investigating ocular blood flow in the choroid may be important to understand the pathogenesis of numerous ocular diseases, such as glaucoma or agerelated macular degeneration (AMD). Laser Doppler flowmetry (LDF) was applied to measure relative velocity, volume and flux of red blood cells in the tissues of human eye. Its main application lies in the possibility of assessing alterations in blood flow early in the course of diseases. The purpose of the present study was to investigate the effect of pupil dilatation with one drop of 1% tropicamide on blood flow in the foveal region of the choroid of the human fundus. The blood flow parameters were measured in 24 eyes during 30 minutes (one measurement in every 3 minutes) after the application of the drop. Since the Doppler parameters depend on the scattering geometry, which may change as the pupil dilates; an artificial pupil of 4mm in diameter was placed directly in front the eye. Following the administration of tropicamide the mean pupil diameter was increased from 3.29 mm to 8.25 mm (PPaired student t-test). In comparison to the baseline values, the data shows no significant increases were observed in velocity, volume, and flow with 4 mm artificial pupil (0.2%, 1.3%, 0.8% respectively) and a statistically significant increases were observed without artificial pupil (10.7%, 13.9%, 12.8% respectively) following the application of tropicamide.

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

2012-03-01

 
 
 
 
201

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

202

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

International Nuclear Information System (INIS)

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 perff 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 ?1, 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.

203

Multi-channel laser Doppler velocimetry using a two-dimensional optical fiber array for obtaining instantaneous velocity distribution characteristics  

Science.gov (United States)

A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.

Kyoden, Tomoaki; Yasue, Youichi; Ishida, Hiroki; Akiguchi, Shunsuke; Andoh, Tsugunobu; Takada, Yogo; Teranishi, Tsunenobu; Hachiga, Tadashi

2015-01-01

204

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

205

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Me...

Arturo Brunetti; Marco Salvatore; Marcello Mancini; Sandra Albanese; Anna Rita Daniela Coda; Matteo Gramanzini; Raffaele Liuzzi; Sara Gargiulo; Adelaide Greco; Monica Ragucci

2012-01-01

206

Material properties identification using ultrasonic waves and laser Doppler vibrometer measurements: a multi-input multi-output approach  

International Nuclear Information System (INIS)

In this paper a multi-input multi-output approach able to determine the material properties of homogeneous materials is presented. To do so, an experimental set-up which combines the use of multi harmonic signals with interleaved frequencies and laser Doppler vibrometer measurements has been developed. A modeling technique, based on transmission and reflection measurements, allowed the simultaneous determination of longitudinal wave velocity, density and thickness of the materials under test with high levels of precision and accuracy. (paper)

207

32×32 pixel array complementary metal-oxide semiconductor imaging sensor for laser Doppler blood-flow measurement  

Science.gov (United States)

A 32×32 pixel array has been fabricated in a 0.35-?m complementary metal-oxide semiconductor process with the aim of producing two-dimensional laser Doppler blood-flow images. In the design, each pixel contains five basic elements: a photodiode, a front-end consisting of a current to voltage converter, voltage amplifier, antialiasing filter, and buffer. The analog design is optimized for the detection of laser Doppler blood-flow signals and thus offers advantages over conventional sensors. The analog outputs are passed through an on-chip multiplexer and digitized by an external analog-to-digital converter. The sensor has been fully characterized electrically and optically using modulated electrical and optical signals. A calibration process for fixed pattern noise reduces the standard deviation of the ac gain by a factor of 2. The imaging response is tested by imaging a vibrating test structure and a rotating diffuser. Blood-flow measurements on a finger before and after occlusion demonstrate that the sensor array is capable of detecting blood-flow signals from tissue. The knowledge gained from the characterization of the design can be used to develop a fully integrated laser Doppler blood-flow sensors with a higher number of pixels.

He, Diwei; Kongsavatsak, Chayut; Hayes-Gill, Barrie R.; Crowe, John A.; Morgan, Stephen P.

2011-05-01

208

Sub-Doppler Two-Photon Laser Spectroscopy of Antiprotonic Helium and the Antiproton-to-Electron Mass Ratio  

International Nuclear Information System (INIS)

The ASACUSA collaboration of CERN has recently irradiated antiprotonic helium atoms with two counter-propagating laser beams. This excited some non-linear two-photon transitions of the antiproton at the deep UV wavelengths ? = 139.8–197.0 nm. The counterpropagating geometry of the laser beams reduced the thermal Doppler broadening of the observed resonances. Their narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3–5 parts in 109. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). (author)

209

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

210

Absorption and scattering coefficient dependence of laser-Doppler flowmetry models for large tissue volumes  

International Nuclear Information System (INIS)

Based on quasi-elastic scattering theory (and random walk on a lattice approach), a model of laser-Doppler flowmetry (LDF) has been derived which can be applied to measurements in large tissue volumes (e.g. when the interoptode distance is >30 mm). The model holds for a semi-infinite medium and takes into account the transport-corrected scattering coefficient and the absorption coefficient of the tissue, and the scattering coefficient of the red blood cells. The model holds for anisotropic scattering and for multiple scattering of the photons by the moving scatterers of finite size. In particular, it has also been possible to take into account the simultaneous presence of both Brownian and pure translational movements. An analytical and simplified version of the model has also been derived and its validity investigated, for the case of measurements in human skeletal muscle tissue. It is shown that at large optode spacing it is possible to use the simplified model, taking into account only a 'mean' light pathlength, to predict the blood flow related parameters. It is also demonstrated that the 'classical' blood volume parameter, derived from LDF instruments, may not represent the actual blood volume variations when the investigated tissue volume is large. The simplified model does not need knowledge of the tissue optical parameters and thus should allow the development of very simple and cost-effective LDF hardware

211

Laser Doppler Blood Flow Imaging Using a CMOS Imaging Sensor with On-Chip Signal Processing  

Directory of Open Access Journals (Sweden)

Full Text Available The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used off-chip cannot be implemented. Therefore the analog signal processing at each pixel is a tailored design for LDBF signals with balanced optimization for signal-to-noise ratio and silicon area. This custom made sensor offers key advantages over conventional sensors, viz. the analog signal processing at the pixel level carries out signal normalization; the AC amplification in combination with an anti-aliasing filter allows analog-to-digital conversion with a low number of bits; low resource implementation of the digital processor enables on-chip processing and the data bottleneck that exists between the detector and processing electronics has been overcome. The sensor demonstrates good agreement with simulation at each design stage. The measured optical performance of the sensor is demonstrated using modulated light signals and in vivo blood flow experiments. Images showing blood flow changes with arterial occlusion and an inflammatory response to a histamine skin-prick demonstrate that the sensor array is capable of detecting blood flow signals from tissue.

Cally Gill

2013-09-01

212

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

213

Endoscopic laser Doppler flowmetry in evaluation of human gastric blood flow  

International Nuclear Information System (INIS)

The aims of the present study were to evaluate laser Doppler flowmetry (LDF) for endoscopic mesasurement of gastric blood flow. The study gave the following results: LDF is a reliable method for continuous measurement of gastrointestinal blood perfusion. This technique can be used endoscopically for measurement of gastric blood flow in conscious man. By means of endoscopic technique, relative blood flow changes can be measured in all parts of the stomach. The recorded blood flow values usually represent blood perfusion in all layers in the gastric wall. A slight contact pressure between the measuring probe and the mucosa is necessary to obtain stable recordings. To heavy pressure provokes reduction of flow values. Angulation of the probe and moderate air insufflation do not interfere with a constant flow level. Endoscopic measurements should be performed with a recording band-width of 4 kHz, since this frequency limit reduces the disturbing signals. Within the range of flow levels recorded in patients and healthy subjects, relative blood flow changes are measured with this band-width. Endoscopic LDF is safe and easy to handle. However, peristalsis and uneasy patients may sometime provoke disturbances which render blood flow measurements impossible. Endoscopic LDF is suitable for clinical studies such as investigation of the effect of drugs on gastric blood flow and examination of local blood flow in patients with gastric diseasesses

214

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

215

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

Science.gov (United States)

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

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

2014-06-01

216

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

International Nuclear Information System (INIS)

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

217

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

218

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

219

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

Science.gov (United States)

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

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

2005-05-01

220

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

 
 
 
 
221

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

222

High-Volume Hydrodissection: Assessment of Deep Inferior Epigastric Perforator Flap Perfusion Using Laser Doppler.  

Science.gov (United States)

High-volume hydrodissection of intramuscular perforators of deep inferior epigastric perforator (DIEP) flaps in Sprague-Dawley rats has previously demonstrated a significant reduction in dissection time while simultaneously increasing the safety of dissection. However, increasing volumes of fluid injected into the closed rectus compartment may have adverse consequences on perfusion to the overlying flap. A prospective experimental animal study was performed to define a safe upper limit of volume injection for high-volume hydrodissection. Eight Sprague-Dawley rats underwent bilateral "DIEP" flap dissections with varying volumes of fluid (1, 3, 6, and 9 mL) injected into the study side. The primary outcome measurement was overlying tissue perfusion, measured using laser Doppler imaging, at 6 separate time points during the flap harvest. Although no significant difference in perfusion was noted between study and control sides despite increasing volumes of injection, a trend toward significant altered perfusion was noted immediately after injection in the 9-mL study group. Six milliliters is defined as the safe upper limit volume of injection into the closed rectus compartment without significantly altering overlying flap perfusion in our Sprague-Dawley rats. Using volumetric analysis, these data translate to 425 mL as the safe upper limit for high-volume hydrodissection for a single average sized human rectus sheath during DIEP flap harvesting. The mechanical and potentially pharmacologic implications of these data in humans remain to be seen. PMID:25003454

Fanzio, Paolo Maria; Cheng, Ming-Huei; Samcam, Ivan; Lin, Yu-Te; Gorantla, Vijay; Lee, Bernard T; Singhal, Dhruv

2014-07-01

223

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

International Nuclear Information System (INIS)

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 2.0x104 to 2.1x105. 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)

224

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

225

NPP power uprates using ultrasonic flowmeter. Middle report on evaluation of techniques of ultrasonic flowmeter  

International Nuclear Information System (INIS)

This report is abstract of the intermediate report on evaluation of techniques of ultrasonic flowmeter published in the 2006 Annual Meeting of the Atomic Energy Society of Japan. The Chordal type, Crossflow type and External type ultrasonic flowmeters are used by measurement uncertainty recapture (MU) uprates. The Chordal type and Crossflow type ultrasonic flowmeter should be evaluated the extrapolation value at the high Reynolds number by experiments. It is possible to increase 0.5% to 1.7% NPP power uprates by MU under the constant stability in Japan. When about 1% NPP power uprates is applied, about 0.5 million kW power is generated. On three kinds of ultrasonic flowmeters, measurement method, principle of measurement, accuracy and evaluation points are shown. (S.Y.)

226

High resolution Doppler lidar based on actively stabilized ring dye laser  

International Nuclear Information System (INIS)

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

227

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

228

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

CERN Document Server

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

Reiners, A; Ulbrich, R G

2014-01-01

229

Vibration transmissibility on rifle shooter: A comparison between accelerometer and laser Doppler vibrometer data  

Science.gov (United States)

The transmission of mechanical vibrations from tools to human subjects is known to be potentially dangerous for the circulatory and neurological systems. It is also known that such damages are strictly depending on the intensity and the frequency range of the vibrational signals transferred to the different anatomical districts. In this paper, very high impulsive signals, generated during a shooting by a rifle, will be studied, being such signals characterised by a very high acceleration amplitude as well as high frequency range. In this paper, it will be presented an experimental setup aimed to collect experimental data relative to the transmission of the vibration signals from the rifle to the shoulder of subject during the shooting action. In particular the transmissibility of acceleration signals, as well as of the velocity signals, between the rifle stock and the subject's back shoulder will be measured using two piezoelectric accelerometers and a single point laser Doppler vibrometer (LDV). Tests have been carried out in a shooting lab where a professional shooter has conducted the experiments, using different experimental configurations: two different types of stocks and two kinds of bullets with different weights were considered. Two uniaxial accelerometers were fixed on the stock of the weapon and on the back of the shoulder of the shooter respectively. Vibration from the back shoulder was also measured by means of a LDV simultaneously. A comparison of the measured results will be presented and the pros and cons of the use of contact and non-contact transducers will be discussed taking into account the possible sources of the measurement uncertainty as unwanted sensor vibrations for the accelerometer.

Scalise, L.; Casacanditella, L.; Santolini, C.; Martarelli, M.; Tomasini, E. P.

2014-05-01

230

A standardized bedside test for assessment of peripheral sympathetic nervous function using laser Doppler flowmetry.  

Science.gov (United States)

In spite of increasing knowledge about the role of the sympathetic nervous system in autonomic disturbances like reflex sympathetic dystrophy, no functional test for the peripheral sympathetic system has been introduced into the clinical routine so far. In the development of a standardized bedside test, effects of arousal stimuli [inspiratory gasp (IG) and contralateral cooling (CC)] on blood flow in the fingertips (FTBF) were studied, using laser Doppler flowmetry (LDF). Fifty-two healthy subjects (ages 17 to 75) and 15 patients with sympathetic reflex dystrophy (SRD) underwent the diagnostic procedure. FTBF of healthy subjects during arousal maneuvers showed a reproducible decrease, which is related to a sympathetic vasoconstrictor response. The standardized test procedure with external body heating made interindividual test results comparable. Examination trials with 4 healthy subjects on 10 subsequent days showed good reproducibility. Mathematical analysis of the LDF curves was performed to calculate the degree of FTBF decrease (SRF = (Fmean - Fmin)/Fmean, QI = integral pre/integral post). In contrast to absolute flow values like Fmean and Fmin or time-related parameters like tdecrease and tregeneration, SRF and QI values presented small coefficients of variation (IG test, SRF 25.7, QI 21.7; CC test, SRF 20.0, QI 15.3). The typical decrease of the LDF signal after sympathetic stimulation was absent or diminished in patients with SRD. SRF and QI values showed statistically highly significant differences (P < 0.001) compared to healthy subjects. The presented test appears reliable for the assessment of peripheral sympathetic nervous function. The narrow physiological range of SRF and QI values enabled the differentiation of pathological sympathetic reactions. The test procedure is easy to perform, noninvasive, and practical even in patients with injuries of the upper limbs. PMID:8901444

Schürmann, M; Gradl, G; Fürst, H

1996-09-01

231

Laser-Doppler flowmetry reveals rapid perfusion changes in adipose tissue of lean and obese females.  

Science.gov (United States)

The present study aimed to evaluate adipose tissue blood flow (ATBF) by means of laser-Doppler flowmetry (LDF) in humans. Lower body negative pressure (LBNP) and straining known to affect epidermal blood flow through the autonomic nervous system were performed in 11 lean and 11 obese female volunteers. ATBF changes were compared between both groups and also discriminated from skin blood flow (SBF) responses of the immediate vicinity. Additionally, LDF measurements were compared with flow measurements using (133)xenon washout in 10 lean subjects during whole body cooling. LDF estimations of SBF and ATBF showed a positive correlation to (133)Xe during cooling. SBF and ATBF were reduced to the same extent in both lean and obese subjects during LBNP. Straining induced divergent changes in SBF and ATBF: initially SBF decreased while ATBF increased, but toward the end of straining SBF increased above baseline and ATBF returned down to baseline level. Those changes were similar in both weight groups. Interestingly, only in obese subjects, both LBNP and straining were followed by ATBF augmentation, while SBF levels remained stable. In conclusion, LDF compares with (133)Xe washout in monitoring ATBF during tonic perfusion changes. Its strength, however, lies in the detection of rapid flow alterations within the subcutaneous tissue, allowing the evaluation of reflex responses of the subcutaneous microcirculation. Interestingly, those rapid changes in SBF and ATBF can be both concordant and discordant. With regard to ATBF, vasoconstrictor components of the reflex responses were similar in lean and obese subjects, whereas vasodilatory responses were more pronounced in obese volunteers. PMID:16787964

Wellhöner, P; Rolle, D; Lönnroth, P; Strindberg, L; Elam, M; Dodt, C

2006-11-01

232

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.)

233

Velocity measurement inside a motored internal combustion engine using three-component laser Doppler anemometry  

Science.gov (United States)

A three-component laser Doppler anemometry (LDA) system has been employed to investigate the structure of the flow inside the cylinder of a motored internal combustion engine. This model engine was reasonably representative of a typical, single cylinder, spark ignition engine although it did not permit firing. It was equipped with overhead valve gear and optical access was provided in the top and side walls of the cylinder. A principal objective was to study the influence of the inlet port design on the flow within the cylinder during the induction and compression strokes of the engine. Here, it can be noted that results obtained in an unfired engine are believed to be representative of the flow behaviour before combustion occurs in a fired engine (see P.O. Witze, Measurements of the spatial distribution and engine speed dependence of turbulent air motion in an i.c. engine, SAE Paper No. 770220, 1977; Witze, Sandia Laboratory Energy Report, SAND 79-8685, Sandia Laboratories, USA, 1979). Experimental data presented for an inclined inlet port configuration reveal the complex three-dimensional nature of the flow inside the model engine cylinder. Not surprisingly, the results also show that the inclined inlet port created flow conditions more favourable to mixing in the cylinder. Specifically, the inclined inlet flow was found to generate a region with a relatively high shear and strong recirculation zones in the cylinder. Inclining the inlet port also produced a more nearly homogeneous flow structure at top dead centre during the compression stroke. The paper identifies the special difficulties encountered in making the LDA measurements. The experimental findings are examined and the problems that arise in presenting time-varying three-dimensional data of this type are discussed. Finally, the future potential of this experimental approach is explored.

Chan, V. S. S.; Turner, J. T.

2000-10-01

234

New on-site calibration technique for large district heating meters using Laser Doppler Velocimetry  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new method of calibrating district heating (DH) meters of 100 to 1000 mm diameter whilst on-site and in operation using Laser Doppler Velocimetry (LDV). The technique has been tested and demonstrated in the laboratory and in the field. Calibration of large DH meters using traditional methods is difficult, if not impossible. It is often a labour demanding, time consuming and costly task to remove and send a meter for off-site calibration. Using LDV for on-site calibration is an attractive alternative. LDV is an established optical technique for measuring point velocity in clear gasses and fluids and is used in a wide range of R and D applications. Using LDV it is now possible to carry out accredited on-site calibration of large DH flow meters with water flow velocities from 0.01 to 6.0 m/s. Using the LDV technique field measurements can be carried out with an uncertainty of {+-}0.9% depending on specific flow conditions and accuracy requirements. Calibration is based on a series of measurements taken over 2 to 4 diameters and optical access to the DH water is obtained by installing specially designed windows close to the flow meter. Point velocity measurements are converted to volume flow rate by using known flow rate estimation techniques. In addition to flow rate estimates the LDV technique can also be utilised to map flow conditions, such as the result of disturbances such as pipe bends and valves. By rotating the LDV measurement instrument about the optical axis the tangential or swirl velocity component can be measured and the degree of swirl and flow disturbance can be mapped. The technique and practical experience from measurements will be presented. Examples of laboratory and field measurements, including examples of flow profiles for non-disturbed and disturbed flow conditions will be given. (orig.)

Drysdale, A.; Frederiksen, J.; Rasmussen, M.A. [Danish Technological Institute, Aarhus (Denmark)

2004-07-01

235

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

International Nuclear Information System (INIS)

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

236

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

237

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

Energy Technology Data Exchange (ETDEWEB)

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{sup ?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., E-mail: dlott@illinois.edu [School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2014-04-15

238

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

239

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)

240

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

 
 
 
 
241

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

Science.gov (United States)

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

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

2003-06-01

242

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

243

Influence of validation schemes in a laser Doppler anemometer period timing device for frequency measurement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The short duration of the Doppler signal and noise content in it necessitate a validation scheme to be incorporated in the electronic processor used for frequency measurement, There are several different validation schemes that can be employed in period timing devices. A detailed study of the influence of these validation schemes on the measured frequency has been reported here. These studies were carried out by using a combination of a fast A/D converter and computer. Doppler bursts ob...

Venkatesh, Prabha

1981-01-01

244

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

Science.gov (United States)

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

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

2014-09-01

245

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...

Ma Hui-Min; Wang Shu-You; Li Shun-Yue; Zhang Dong

2011-01-01

246

[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

247

Contactless Electromagnetic Phase-Shift Flowmeter for Liquid Metals  

CERN Document Server

We present a concept and test results of an induction flowmeter for liquid metals. The flow rate is determined by applying a weak AC magnetic field to a liquid metal flow and measuring the flow-induced phase disturbance in the external electromagnetic field. The phase disturbance is found to be more robust than that of the amplitude used in conventional AC flowmeters. The basic characteristics of this type of flowmeter are analysed using simple theoretical models where the flow is approximated by a solid body motion. Design of such a flowmeter is presented and its test results reported.

Priede, J?nis; Gerbeth, Gunter

2010-01-01

248

A study of air-coupled ultrasonic flowmeter  

International Nuclear Information System (INIS)

A non-contact flowmeter employing air-coupled ultrasonic is developed in this study. Flow rate of feed water and cooling water for the condenser are monitored to control the thermal output of the nuclear reactor. Ultrasonic flowmeter has an advantage in its accuracy compared with differential pressure flowmeter and venturi flowmeter. However, the performance of sensors decreases in high-temperature conditions such as nuclear power plants and thermal power plants, and measuring accuracy declines because a sensor lose a piezoelectricity over its Curie point. (author)

249

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

Science.gov (United States)

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

Crua, Cyril; Heikal, Morgan R.

2014-12-01

250

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

251

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

International Nuclear Information System (INIS)

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

252

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

Science.gov (United States)

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

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

2014-05-01

253

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

International Nuclear Information System (INIS)

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

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

Laser-Doppler velocimeter for measuring droplet velocities in two-phase liquid-dominated nozzle flows  

Energy Technology Data Exchange (ETDEWEB)

A new laser-Doppler velocimeter (LDV) arrangement for measuring droplet velocities in high velocity, liquid-dominated two-phase nozzle flows was developed. The transmitting optics arrangement for this LDV system is identical to that of a dual beam heterodyne LDV, i.e., the light beam from a single frequency argon laser is divided into two parallel identical beams, which are focused to an intersection volume in the flow. The light backscattered from droplets traveling through this volume is collected for analysis using a scanning confocal Fabry-Perot interferometer (FPI). Because of the dual beam arrangement an unscattered or reference beam is not necessary, and the optical alignment ease and stability are greatly improved over similar LDV-FPI systems. Results of droplet velocity measurements in high velocity, high droplet concentration nozzle jet flows are presented.

Alger, T.W.; Crowe, C.T.; Giedt, W.H.

1978-01-01

256

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

International Nuclear Information System (INIS)

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

257

Transcutaneous Doppler ultrasound measurement of superior mesenteric artery blood flow in man.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A duplex scanner which consists of a real time two dimensional scanner and a pulsed Doppler flowmeter was used to measure superior mesenteric blood flow in 70 healthy subjects. By processing the Doppler shift signals, the instantaneous average Doppler shift frequency and then the instantaneous average velocity of the flow rate were calculated. Both diameter of the vessel and angle between vessel and beam were measured from real time imaging. The mean (+/- standard error of the mean) of the su...

Qamar, M. I.; Read, A. E.; Skidmore, R.; Evans, J. M.; Wells, P. N.

1986-01-01

258

Slug flow measurement using a current-sensing electromagnetic flowmeter  

International Nuclear Information System (INIS)

In order to investigate the characteristics of two-phase slug flow, a current-sensing electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. Theory of a current-sensing electromagnetic flowmeter with high temporal resolution was also developed. A flow pattern coefficient and a localization parameter were introduced for developing two-phase flow. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under singlephase flow was ±2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble

259

The study of the flow in an helico-axial pump using laser doppler velocimetry; Exploration par anemometrie laser doppler de l'ecoulement dans une pompe helico-axiale  

Energy Technology Data Exchange (ETDEWEB)

The increasing interest in the development of multiphase flow pumping and the performances in cavitating regime characterising inducers, partially incited the Institut Francais du Petrole (IFP) to develop rotors of the same type as the one equipping the pump of the actual study with a configuration similar to that of inducers. This paper presents the work led within the framework of the experimental study of multiphase flow in turbomachinery. We present the results obtained by Laser Doppler velocimetry in the rotor of an helico-axial pump. Before starting the study in a multiphase environment, it was interesting, at first, to understand the nature of the flow with a single phase fluid. The measurements synchronized with the angular position of the rotor, allowed to restore the relative flow and thus to access to a better understanding of the flow structure in the inducers. (authors)

El Hajem, M.; Morel, R.; Champagne, J.Y. [Institut National des Sciences Appliquees (INSA), 69 - Villeurbanne (France)

2001-07-01

260

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

Directory of Open Access Journals (Sweden)

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

Pape Sarah A

2009-02-01

 
 
 
 
261

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.

262

Continuous postoperative lCBF monitoring in aneurysmal SAH patients using a combined ICP-laser Doppler fiberoptic probe.  

Science.gov (United States)

Cerebral vasospasm remains the principal cause of morbidity and mortality following successful clipping of intracranial aneurysms. Current management often requires subjective judgments concerning presumed abnormalities of cerebral blood flow. In this study, a combined intracranial pressure (ICP)-laser Doppler flowmetry (LDF) fiberoptic probe that permits continuous monitoring of local cerebral blood flow (lCBF) was used in the postoperative management of 20 aneurysm patients. Using this probe, lCBF was simultaneously recorded and integrated on a real time basis with other physiological parameters, including ICP, systemic arterial pressure, pulmonary arterial pressure, central venous pressure, and pulse oximetry. The combined probe also provided the ability to obtain precise and detailed information concerning the presence or absence of cerebral autoregulation and CO2 vascular reactivity, and allowed calculation of the cerebral vascular resistance. Continuous monitoring of lCBF in this manner complemented by transcranial Doppler and angiographic data permitted early detection of cerebral ischemia, helped to differentiate cerebral ischemia from edema and hyperemia, was useful in titrating blood pressure and fluid management, provided direct feedback about the effectiveness of instituted therapies, and determined early on when medical management was of no avail and that interventional neuroradiology was indicated. Evidence is presented that the presence of angiographic vasospasm and increased velocities on TCD do not always correlate with ischemia in the microcirculation and that direct measurements of lCBF are often at variance with calculations of cerebral perfusion pressure (CPP). PMID:8803831

Johnson, W D; Bolognese, P; Miller, J I; Heger, I M; Liker, M A; Milhorat, T H

1996-07-01

263

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

Science.gov (United States)

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

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

1989-01-01

264

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

Science.gov (United States)

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.

Binzoni, Tiziano; Sekhar Seelamantula, Chandra; Van De Ville, Dimitri

2010-07-01

265

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

International Nuclear Information System (INIS)

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)

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

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

Science.gov (United States)

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

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

2012-11-01

268

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

International Nuclear Information System (INIS)

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

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)

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

Intercomparison of laser Doppler wind measurements with other methods and a forecast model  

Science.gov (United States)

The wind field over sea can be determined with an ERS-satellite by synthetic aperture radar (SAR) with an accuracy of about 0963-9659/7/6/024/img9 and 0963-9659/7/6/024/img10 using the ESA CMOD4 algorithm. Wind profiles were measured by the airborne Doppler lidar ADOLAR. A first comparison in a few levels (surface up to 1200 m above sea) was performed. During an experiment near the island of Rügen a synophic SAR/ADOLAR dataset was acquired. An analysis of the dataset comparing to ground truth and the DWD analysis was performed.

Werner, Christian; Rahm, Stephan; Lehner, Susanne; Buchhold, Michael; Banakh, Victor; Smalikho, Igor

1998-11-01

272

Wavelength modulation diode laser absorption signals from Doppler broadened absorption profiles  

International Nuclear Information System (INIS)

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

273

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

274

Investigations of unsteady flow in the draft tube of the pump- turbine model using laser Doppler anemometry  

Science.gov (United States)

The measurements and video observation of unsteady flow in the draft tube cone of the pump-turbine model were conducted in the Laboratory of Water Turbines, property of OJSC "Power machines" - "LMZ". The prototype head was about 250 m. The experiments were performed for the turbine mode of operation. Measurements were taken for the unit speed value n11 corresponding to rated head in the generating mode of operation, for a wide range of guide vanes openings at loads ranging from partial to maximum value. The researches of the velocity field in function of the Thoma number were carried out in some operating conditions. The mean values and RMS deviations of the velocity components were the results of laser measurements. The curves of the intensity of the vortex versus the guide vane opening and the Thoma number were plotted. The energy velocity spectra were presented for the points at which the most pronounced frequency precession of the helical axial vortex was observed. Video recording and laser Doppler anemometry were made in the operating conditions of the developed cavitation. Based on the results of video observations and energy spectra obtained via LDA, vortex frequencies were determined i.e. the frequencies of the vortex precession under the runner in the draft tube cone.

Kaznacheev, A.; Kuznetsov, I.

2014-12-01

275

Acute Effects of Vascular Modifying Agents in Solid Tumors Assessed by Noninvasive Laser Doppler Flowmetry and Near Infrared Spectroscopy  

Directory of Open Access Journals (Sweden)

Full Text Available The potential of noninvasive laser Doppler flowmetry (LDF and near infrared spectroscopy (NIRS to detect acute effects of different vascular-modifying agents on perfusion and blood volume in tumors was evaluated. C3H mouse mammary carcinomas (?200 mm3 in the rear foot of CDF1 mice were treated with flavone acetic acid (FAA, 150 mg/kg, 5,6-dimethylxanthenone-4acetic acid (DMXAA, 20 mg/kg, combretastatin A-4 disodium phosphate (CAMP, 250 mg/kg, hydralazine (HDZ, 5 mg/kg, or nicotinamide (NTA, 500 mg/kg. Tumor perfusion before and after treatment was evaluated by noninvasive LDF, using a 41°C heated custombuilt LDF probe with four integrated laser/receiver units, and tumor blood volume was estimated by MRS, using light guide coupled reflectance measurements at 800±10 nm. FAA, DMXAA, CAMP, and HDZ significantly decreased tumor perfusion by 50%, 47%, 73%, and 78%, respectively. In addition, FAA, DMXAA, and HDZ significantly reduced the blood volume within the tumor, indicating that these compounds to some degree shunted blood from the tumor to adjacent tissue, HDZ being most potent. CAMP caused no change in the tumor blood volume, indicating that the mechanism of action of CAMP was vascular shut down with the blood pool trapped in the tumor. NTA caused no change in either tumor perfusion or tumor blood volume. We conclude that noninvasive LDF and MRS can determine acute effects of vascular modifying agents on tumor perfusion and blood volume.

Michael Kragh

2002-01-01

276

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

2007-02-01

277

Nd:YAG laser bloodless tonsillectomy by fiber optic doppler coupled handpiece beam delivery  

Science.gov (United States)

Laser ablation of palatine tonsils is a relatively new technique recently performed in head and neck surgery departments, in order to treat recurrent tonsillar infections or obstructions from enlarged tonsils. In our study, we have investigated a new procedure using the fiber optic laser beam Nd:YAG to remove up to the 89% of tonsillar tissue, and leaving in place the capsule avoiding any hemorrhagic complication and limiting the pain.

Palmieri, Beniamino; Rottigni, Valentina

2012-09-01

278

Accuracy of Medical Oxygen Flowmeters: A Multicentric Field Study  

Directory of Open Access Journals (Sweden)

Full Text Available The accuracy of 476 oxygen flowmeters was investigated using a thermal mass flowmeter in eight hospitals in France and Belgium. Different oxygen flow rates (2 to 15 l/min were evaluated at the patient’s bed. When the sample was considered as a whole, the accuracy of delivered flow was acceptable but precision was poor. The variability of the delivered flow between devices was greater when a low flow rate was required. Compensated-pressure oxygen flowmeters for these low rates were more accurate than their non-compensated counterparts. This study emphasizes the need to individually adapt the oxygen flow rate each time a patient has to move from one flowmeter to another.

Frédéric Duprez

2014-08-01

279

Inductive flowmeter for electrically conductive media  

International Nuclear Information System (INIS)

The flowmeter consists of two tubes arranged coaxially with respect to one another, being electrically connected with one another by means of steadying struts. Through the interspace conductive media are flowing, the surfaces of the two tubes which are in contact with the medium being electrically insulated. A magnetic field is penetrating both tubes vertically with respect to the axis of the two tubes. The outer tube consists of nonmagnetic, the inner one of magnetic material. There may be detected small flow rates, because on one hand the length of the electric conductor filament has been increased and on the other, the length of the lines of magnetic flux within the nonmagnetic tube was decreased. (DG)

280

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.)

 
 
 
 
281

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

282

Geschwindigkeitsmessungen im Downcomer der ROCOM Versuchsanlage mittels Laser-Doppler Anemometrie im Vergleich mit numerischen Berechnungen  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An der Vermischungsanlage ROCOM, einem 1:5 skalierten Modell des Druckwasserreaktors Konvoi wurden umfangreiche Geschwindigkeitsmessungen im Downcomer des Reaktordruckbehälters für verschiedene Schleifendurchsätze und Teilschleifenbetrieb durchgeführt. Durch Verwendung eines leistungsfähigen Lasers konnten auch transiente Geschwindigkeitsprofile aufgenommen werden. Einige der gemessenen Profile wurden mit dem numerischen Strömungsberechnungsprogramm CFX-4 nachgerechnet. Bei Vierschlei...

Grunwald, Gerhard; Ho?hne, Thomas; Prasser, Horst-michael

2010-01-01

283

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

284

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 “Ox...

Hans-Martin Sommer; Gereon Berschin; Björn Sommer

2013-01-01

285

Monitoring Hypoxia Induced Changes in Cochlear Blood Flow and Hemoglobin Concentration Using a Combined Dual-Wavelength Laser Speckle Contrast Imaging and Doppler Optical Microangiography System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A synchronized dual-wavelength laser speckle contrast imaging (DWLSCI) system and a Doppler optical microangiography (DOMAG) system was developed to determine several ischemic parameters in the cochlea due to a systemic hypoxic challenge. DWLSCI can obtain two-dimensional data, and was used to determine the relative changes in cochlear blood flow, and change in the concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (Hb) and total hemoglobin (HbT) in mice. DOMAG can obtain three-dimensiona...

Reif, Roberto; Qin, Jia; Shi, Lei; Dziennis, Suzan; Zhi, Zhongwei; Nuttall, Alfred L.; Wang, Ruikang K.

2012-01-01

286

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

287

Changes in Carotid Artery Flow Velocities after Stent Implantation A Fluid Dynamics Study with Laser-Doppler-Anemometry and a US guidewire  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: To study the influence of stents positioned at various locations in a physiological model of the carotid artery on the flow behaviour. Methods: Wallstents (Boston Co.) were positioned in silicon models of the carotid artery at various locations: entirely in the internal carotid artery (ICA), in the ICA extending partially and completely into the bulb, and in the ICA extending completely into the commun carotid artery (CCA). Measurements were performed with Laser-Doppler-Anemometry (L...

Greil, Oliver

2007-01-01

288

Measurements with laser-doppler-anemometry of fluid-flow in a model of the bifurcation of a human carotid artery using three different cerebral protective devices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The endovascular reconstruction of the bifurcation of the carotid artery is done under open blood flow. In order to minimize the risk of cerebral embolization during the intervention so called neuroprotective devices are used temporarily. Using laser-doppler-anemometry, the effects of those protective devices (three different devices: FilterWire, Rx AccuNet, EmboShield) on fluid mechanics were examined in a model of the carotid artery. The physiological flow-profile was reproduced precisely, ...

Patzelt, Johannes

2009-01-01

289

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

International Nuclear Information System (INIS)

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

290

Multiscale Compression Entropy of Microvascular Blood FlowSignals: Comparison of Results from Laser Speckle Contrastand Laser Doppler Flowmetry Data in Healthy Subjects  

Directory of Open Access Journals (Sweden)

Full Text Available Microvascular perfusion is commonly used to study the peripheral cardiovascular system. Microvascular blood flow can be continuously and non-invasively monitored with laser speckle contrast imaging (LSCI or with laser Doppler flowmetry (LDF. These two optical-based techniques give perfusion values in arbitrary units. Our goal is to better understand the perfusion time series given by each technique. For this purpose, we propose a nonlinear complexity analysis of LSCI and LDF time series recorded simultaneously in nine healthy subjects. This is performed through the computation of their multiscale compression entropy. The results obtained with LSCI time series computed from different regions of interest (ROI sizes are examined. Our findings show that, for LSCI and LDF time series, compression entropy values are less than one for all of the scales analyzed. This suggests that, for all scales, there are repetitive structures within the data fluctuations. Moreover, at the largest scales studied, LDF signals seem to have structures that are different from those Entropy 2014, 16 5778 of Gaussian white noise. By opposition, this is not observed for LSCI time series computed from small ROI sizes

Anne Humeau-Heurtier

2014-11-01

291

Turbulence structural measurements using a comprehensive laser-Doppler velocimeter in two- and three-dimensional turbulent boundary layers  

International Nuclear Information System (INIS)

The advanced 'comprehensive' laser-Doppler velocimeter is used to acquire spatially and temporally resolved turbulence structural measurements in high Reynolds number two- and three-dimensional turbulent boundary layers. The new instrument directly measures three-dimensional particle trajectories at high repetitions. These trajectories are analyzed in post-processing to obtain fluctuating velocity gradient tensor fields, which lead to direct measurements of turbulent viscous dissipation rates. Such data acquired in two- and three-dimensional boundary layers with an approach flow momentum thickness Reynolds number, Re? = 7500 are presented. Results indicate that anisotropy of the dissipation rate of Reynolds stresses persists to similar heights in viscous wall units as obtained with direct numerical simulations at lower Reynolds numbers. Measurements in a three-dimensional turbulent boundary layer in the vicinity of a wing/body junction also indicate that a reduction in the value of the velocity/pressure-gradient correlations for the Reynolds normal stresses reduces the turbulent energy redistribution and contributes to reduced shear stress magnitudes, as observed previously through DNS (Moin, P., Shih, T.-H., Driver, D., Mansour, N.N., 1990. Direct numerical simulation of a three-dimensional turbulent boundary layer, Phys. Fluids A 2 (10), 1846-1853)

292

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

International Nuclear Information System (INIS)

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.

293

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

Science.gov (United States)

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

Mickan, B.; Strunck, V.

2014-10-01

294

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

295

Velocity dependence of impact line-broadening studied by resonant Doppler-free two-photon laser spectroscopy  

International Nuclear Information System (INIS)

The velocity dependence of the collision broadening of the 40Ca 4s2 1S0 ? 4s5p 1P1 ? 4s17d1D2 transition by neon atoms has been studied. The experiment was performed exciting one velocity group of Ca atoms within the Doppler profile of the first transition and probing this group with a counterpropagating laser beam inducing the second transition. Using thermionic detection we have measured broadening rates for relative velocities between Ca and Ne atoms which corresponds to a temperature range of about 850 K (cell temperature) to 3000 K. The measured line-width was found to have very weak temperature dependence. This is attributed to the weak velocity dependence of polarization broadening of the final level which was found to be the major contribution to the broadening of the two-photon line. For large relative velocities significant asymmetries in the measured line profiles due to velocity changing collisions had to be taken into account. (orig.)

296

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

Science.gov (United States)

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

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

2008-07-01

297

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-10-21

298

Continuous measurement of cerebral cortical blood flow by laser-Doppler flowmetry in a rat stroke model  

International Nuclear Information System (INIS)

Laser-Doppler flowmetry (LDF), a new method allowing instantaneous, continuous, and noninvasive measurements of microcirculatory blood flow in a small tissue sample, was evaluated for its accuracy in monitoring regional cerebral blood flow (rCBF) in the cortical microcirculation after focal cerebral ischemia. Wistar and spontaneously hypertensive rats (SHR, n = 19) were subjected to permanent occlusion of the middle cerebral and common carotid arteries. Absolute rCBF in a tissue sample of the ischemic hemisphere was measured autoradiographically with [14C]iodoantipyrine as a tracer and compared to rCBF measured by LDF. Additionally, the percent change in rCBF between baseline and ischemic values was compared for both methods. Absolute rCBF values recorded with LDF correlated poorly (r = 0.54) with [14C]iodoantipyrine measurements. In contrast LDF readings expressed as a percentage of ischemic vs. preocclusion readings (relative LDF readings) correlated very well (r = 0.91) with the percent change in [14C]iodoantipyrine measurements. We conclude that LDF does not provide accurate measurements of absolute rCBF values but this method allows accurate measurements of changes in rCBF due to induction of focal cerebral ischemia

299

Laser Echosclerotherapy of varicose veins with haemodynamic echo-doppler evaluation : some rationale and short-term outcomes  

Science.gov (United States)

Purpose: The aim is to verify short-term results in Endovenous Laser Treatment (EVLT) performed in haemodynamic way in patients belonging to C2, C3 classes and type I, II, III venous shunts, according respectively with CEAP and Teupitz classification. Methods: Minor changes of technique were applied to EVLT in order to provide haemodynamic conditions. Treatment efficacy, anatomical failure, complications, recurrence rate and clinical improvements were analyzed. 105 limbs were treated from November 2004 to November 2007. Clinical and Echo-Colour-Doppler (ECD) follow up was performed two weeks, one, two and three years after the surgery. Results: in 79 inferior limbs follow-up was concluded and this are the final data: a) no Deep Venous Thrombosis (DVT) was detected; b) a notable reduction of recurrence if compared with groin recurrence rate in traditional stripping; e) satisfactory cosmetic results and short recovery were found in all the patients. Conclusions: In selected patients haemodynamic-guided EVLT is equally safe and efficient than standard. Clinical and aesthetical outcomes are durable without statistical differences on the plan of disease progression and complications. The recurrence rate is lower in EVLT haemodynamic-guided surgery than in conventional stripping. Long-term outcomes should be investigated. We need studies camparison among the three different kind of surgery performed in haemodynamic way

Vettorello, Gianfranco; Marini, Leonardo

2009-06-01

300

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)

 
 
 
 
301

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)

302

Effects of acupuncture at the Hoku acupoint on the pulsatile laser Doppler signal at the heartbeat frequency.  

Science.gov (United States)

We aimed to assess the effects of acupuncture by analyzing the alternating current (AC) component of skin blood-flow signals (around the heartbeat frequency) simultaneously recorded at the Hoku acupoint, which is an important acupoint in oriental medicine, and two nearby non-acupoints following acupuncture stimulation (AS). Laser Doppler flowmetry signals were measured in 28 experiments on nine volunteers. Each experiment involved the recording of a 20-min control-data sequence and two sets of effects data recorded 0-20 min and 50-70 min after the AS had been stopped. The direct current (DC) and AC components (DCflux and ACflux, respectively), pulse width (PW), and foot delay time (FDT) of the flux signal were calculated. The DCflux, ACflux, PW, and FDT were all significantly increased only at Hoku following AS. Regression analysis between the DCflux and ACflux revealed that the slope was largest (>1) at Hoku among the measurement sites. Our results indicated that both the DCflux and ACflux in the microcirculatory perfusion were increased by stimulation at the Hoku acupoint, with the change being greatest for the latter. Parameters calculated from the pulsatile flux waveform, such as the PW and FDT, could contribute to noninvasive evaluations of the sympathetic neural activities and of the improvement in perfusion following AS. PMID:18780139

Hsiu, Hsin; Hsu, Wei-Chen; Hsu, Chia-Liang; Jan, Ming-Yie; Wang-Lin, Yuh-Ying

2009-07-01

303

Observation of Doppler sidebands of a laser-cooled Ca+ ion by using a low-temperature-operated laser diode  

Science.gov (United States)

The 729-nm radiation obtained from a commercially available laser diode operated at a low temperature was used to observe the S1/2-D5/2 electric-quadrupole-allowed transitions of a laser-cooled Ca+ ion in a small rf trap. The electron shelving method was used to measure the absorption spectrum of the electric-quadrupole-allowed transitions, and the motional sidebands due to the secular motion of the ion in the harmonic potential well of the rf trap were completely resolved. The effective temperature of the ion, estimated by comparing the observed sideband intensities with the theoretical ones, was less than 4.4 mK. This result is in good agreement with that obtained from the analysis of the linewidth measurement.

Urabe, S.; Watanabe, M.; Imajo, H.; Hayasaka, K.; Tanaka, U.; Ohmukai, R.

1998-08-01

304

The improvement of meter performance of EM sensing flowmeters using software modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis is focused on the improvement of the meter performance and power consumption of non-mechanical flowmeters such as the conventional electromagnetic flowmeter and the fluidic oscillator. Each flowmeter is studied using Finite Element Modelling for the magnetic field, the virtual current and the fluid dynamics in order to simulate flow signal. The meter design of the conventional electromagnetic flowmeter is modified to provide a better signal level by optimising th...

Lim, Sungtaek

2008-01-01

305

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

Science.gov (United States)

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.

Cooper, W. A.; Spuler, S. M.; Spowart, M.; Lenschow, D. H.; Friesen, R. B.

2014-03-01

306

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

Directory of Open Access Journals (Sweden)

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

W. A. Cooper

2014-09-01

307

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

Science.gov (United States)

We have experimentally studied electromagnetically induced transparency (EIT) and absorption (EIA) in hot 85Rb atomic vapor using probe and coupling light with comparable power levels. We have shown that strong-probe EIT has different linewidth and appears in fewer configurations than does usual, weak probe EIT. In V-scheme, where optical pumping and saturation are dominant mechanisms, narrow EIT is possible only when a probe is tuned to a closed transition. The width of the EIT resonance increases with laser intensity with non-linear dependence, similar to the weak-probe EIT in Lambda- scheme. The EIT in Lambda- scheme was observed when two transitions had balanced population losses. The EIA was modified for the case of a strong probe as well: in four-level N-scheme with Zeeman sublevels the EIA was observed only for a cycling transition when F'=F+1, where F and F' are the angular momenta of the 5 2S1/2 (ground) and 5 2P3/2 (excited) state hyper-fine levels, respectively. The combination of strong probe and strong coupling laser beam intensities allows observation of an absorption dip due to three-photon resonance in a four-level scheme that involves the Raman transitions via virtual level. PMID:19495020

Krmpot, Aleksandar; Mijailovi?, Marina; Pani?, Bratimir; Luki?, Dragan; Kovacevi?, Aleksander; Panteli?, Dejan; Jelenkovi?, Branislav

2005-03-01

308

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

309

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

Science.gov (United States)

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

Cooper, W. A.; Spuler, S. M.; Spowart, M.; Lenschow, D. H.; Friesen, R. B.

2014-09-01

310

Permanent magnet flowmeter probes, sensors for instrumentation of LMFBR's  

International Nuclear Information System (INIS)

The purpose of this work is the development of a simple sensor for the measurement of velocity and mass flow of liquid metal in test rigs and in LMFBR's. For this purpose permanent magnet flowmeter probes have been developed. The probes have a good long-time temperature stability and they are not influenced on irradiation by fast neutrons. They also operate highly independent of the magnetic strength on the basis of transit time measurement methods. Up to now the flowmeter probes have been already tested and worked in many test rigs and reactor applications such as: Mol 7C, VIC, TOP, CABRI. Presently two probes serve as fuel element flowmeter in the KNK II reactor. Finally the performance of double magnet miniature probes (2 mm O.D.) are presented

311

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

312

Analysis of laser speckle contrast images variability using a novel empirical mode decomposition: comparison of results with laser Doppler flowmetry signals variability.  

Science.gov (United States)

Laser Doppler flowmetry (LDF) and laser speckle contrast imaging (LSCI) have emerged as non invasive optical modalities to monitor microvascular blood flow. Many studies proposed to extract physiological information from LDF by analyzing signals variability. By opposition, such analyses for LSCI data have not been conducted yet. We propose to analyze LSCI variability using a novel data-driven method: the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN). CEEMDAN is suitable for non linear and non stationary data and leads to intrinsic mode functions (IMFs). It is based on the ensemble empirical mode decomposition (EEMD) which relies on empirical mode decomposition (EMD). In our work the average frequencies of LSCI IMFs given by CEEMDAN are compared with the ones given by EMD and EEMD. Moreover, LDF signals acquired simultaneously to LSCI data are also processed with CEEMDAN, EMD and EEMD. We show that the average frequencies of IMFs given by CEEMDAN depend on the signal to noise ratio (SNR) used in the computation but, for a given SNR, the average frequencies found for LSCI are close to the ones obtained for LDF. By opposition, EEMD leads to IMFs with frequencies that do not vary much when the SNR level is higher than a threshold. The new CEEMDAN algorithm has the advantage of achieving a complete decomposition with no error in the reconstruction but our study suggests that further work is needed to gain knowledge in the adjustment of the added noise level. CEEMDAN, EMD and EEMD are data-driven methods that can provide a better knowledge of LSCI. PMID:25347875

Humeau-Heurtier, Anne; Abraham, Pierre; Mahe, Guillaume

2014-10-22

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

What's behind the mask? A look at blood flow changes with prolonged facial pressure and expression using laser Doppler imaging.  

Science.gov (United States)

Clinically, the initial blanching in burn scar seen on transparent plastic face mask application seems to diminish with time and movement requiring mask alteration. To date, studies quantifying perfusion with prolonged mask use do not exist. This study used laser Doppler imaging (LDI) to assess perfusion through the transparent face mask and movement in subjects with and without burn over time. Five subjects fitted with transparent face masks were scanned with the LDI on four occasions. The four subjects without burn were scanned in the following manner: 1) no mask, 2) mask on while at rest, 3) mask on with alternating intervals of sustained facial expression and rest, and 4) after mask removal. Images were acquired every 3 minutes throughout the 85-minute study period. The subject with burn underwent a shortened scanning protocol to increase comfort. Each face was divided into five regions of interest for analysis. Compared with baseline, mask application decreased perfusion significantly in all subjects (P < .0001). Perfusion did not change during the rest period. There were no significant differences with changing facial expression in any of the regions of interest. On mask removal, all regions of the face demonstrated a hyperemic effect with the chin (P = .05) and each cheek (P < .0001) reaching statistical significance. Perfusion levels did not return to baseline in the chin and cheeks after 30 minutes of mask removal. Perfusions remain constantly low while wearing the face mask, despite changing facial expressions. Changing facial expressions with the mask on did not alter perfusion. Hyperemic response occurs on removal of the mask. This study exposed methodology and statistical issues worth considering when conducting future research with the face, pressure therapy, and with LDI technology. PMID:20453735

Van-Buendia, Lan B; Allely, Rebekah R; Lassiter, Ronald; Weinand, Christian; Jordan, Marion H; Jeng, James C

2010-01-01

315

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

316

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 opposis of Reynolds shear stress show the opposite sign region, which is owing to streamwise velocity distorted by secondary flow. (author)

317

Speckle noise influence on measuring turbulence spectra using time-resolved Doppler global velocimetry with laser frequency modulation  

International Nuclear Information System (INIS)

A novel Doppler global velocimeter (DGV) with high temporal resolution is presented as a tool for measuring spatially resolved flow turbulence spectra for three components in order to characterize complex flows, e.g. in turbomachines. The proposed DGV technique is based on a sinusoidal laser frequency modulation. Its maximum available measurement rate equals the modulation frequency and amounts currently to 100 kHz. The harmonic analysis of the detector array signals reduces errors due to detector offset drifts, detector sensitivity changes, ambient light, camera misalignment and beam splitting errors in comparison with conventional DGV systems. The achievable statistical errors are considered by theoretical investigations and by experiments regarding detector noise as well as temporal and spatial scattered light fluctuations, e.g. due to speckles. An error propagation finally provides the determination of the noise power spectral density occurring as virtual turbulence in the measured turbulence spectra. It amounts to about 1.2 × 10?4 (m2 s?2) Hz?2 for mean flow velocities up to 40 m s?1 and 1 nW mean scattered light power per detector element. It rises for higher flow velocities in dependence on the flow turbulence. For the example of a nozzle flow with a mean velocity of 85 m s?1, which is disturbed by a cylinder, the final uncertainty is demonstrated to result in an effective bandwidth oflt in an effective bandwidth of the acquired turbulence spectra of 10 kHz and is thus sufficiently high for flow turbulence analysis. The measured velocity spectra agree well with comparison measurements using a hot-wire anemometer

318

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 137mBa produced in a portable isotope generator. Because of the short half-life (2.6 min) of 137mBa 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

319

Integrated microfluidic flowmeter based on a micro-FBG inscribed in Co²?-doped optical fiber.  

Science.gov (United States)

A novel microfluidic flowmeter integrated with microfiber Bragg grating (µFBG) is presented. Two glass capillaries and a short length of high-light-absorption Co²?-doped optical fiber were stacked inside a larger outer capillary tube. The stack was then drawn into a tapered device. Two microchannels with the diameter of ~50???m were formed inside the capillaries for flowing of microfluidics. An FBG was inscribed in the tapered Co²?-doped fiber with waist diameter of ~70???m, and acts as a flow-rate sensor. A pump laser with wavelength of 1480 nm was utilized to locally heat the µFBG, rendering the µFBG as miniature "hot-wire" flowmeter. The flow rate of the liquid in the microchannels is determined by the induced wavelength shift of the µFBG. The experimental results achieve a minimum detectable change of ~16??nL/s in flow rate, which is very promising in the use as part of biochips. PMID:25361108

Liu, Zhengyong; Tse, Ming-Leung Vincent; Zhang, A Ping; Tam, Hwa-Yaw

2014-10-15

320

Calibration and testing of selected portable flowmeters for use on large irrigation systems  

Science.gov (United States)

Existing methods for measuring discharge of irrigation systems in the High Plains region are not suitable to provide the pumpage data required by the High Plains Regional Aquifer System Analysis. Three portable flowmeters which might be suitable for obtaining fast and accurate discharge measurements on large irrigation systems were tested. A propeller type gaged-pipe meter, a Doppler meter, and a transient-time meter were tested under both laboratory and field conditions during 1979. The gated-pipe meter was found to be difficult to use and sensitive to particulate matter in the fluid. The Doppler meter, while easy to use, would not function on steel pipe 6 inches or larger in diameter, or on aluminum pipe larger than 8 inches in diameter. The transient-time meter was more difficult to use than the other two meters; however, this instrument provided a high degree of accuracy and reliability under a variety of conditions. Of the three meters tested, only the transient-time meter was found to be suitable for providing reliable discharge measurements on the variety of irrigation system used in the High Plains region. (USGS)

Luckey, Richard R.; Heimes, Frederick J.; Gaggiani, Neville G.

1980-01-01

 
 
 
 
321

Study on the development and the application of ultrasonic gas flowmeter  

International Nuclear Information System (INIS)

This paper describes tile 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. In this study, we have developed the signal processing algorithm for the transmitting and receiving method of ultrasonic wave and the ultrasonic signal processing to develop 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.

322

Measurement of blood flow velocity in a model of stenosis in vitro and in mesenteric vessels in vivo using non-invasive micro multipoint laser Doppler velocimetry  

International Nuclear Information System (INIS)

Our research goal is to carry out two-dimensional (2D) and three-dimensional (3D) measurements of the velocity distribution within a single vessel. We modified a non-invasive beam laser Doppler velocimeter using near-infrared light, and linearized the laser to carry out simultaneous multipoint measurements. We also scanned the measurement line in the direction of depth to allow 3D imaging of vascular blood flow in opaque areas in vivo. We used micro multipoint laser Doppler velocimetry (LDV) and a device with improved spatial resolution from 250 to 125 µm. We compared actual and calculated values using a rotating disk with an attached microwire. To demonstrate the effectiveness of the proposed system, blood flowing at a constant rate through a glass capillary and the velocity distribution of flow in the capillary were measured and mapped. The average flow velocity was calculated from the cross-sectional area and flow rate in the glass capillary, and we compared the calculated and measured values. To obtain an image of blood flow velocity in vivo, we measured both 2D and 3D flow velocity distributions in mouse mesenteric vessels. (paper)

323

Measurements of the electrophoretic mobility with a new laser Doppler cytopherometer (Lazypher) and critical evaluation of the electrophorese mobility-test (EMT)  

International Nuclear Information System (INIS)

The new developed Laser Doppler Cytopherometer (Lazypher) allows the exact and objective measurement of the electrophoretic mobility of particles. Comparative experiments with the Free Flow Cell Electrophoresis instrument of Hannig showed identical results. The impression that the electrophoretic Mobility Test (EMT) is not valid for cancer diagnosis has been substantiated. But in its present form with the new instrument (Lazypher) possible improvements, e.g. isolation of lymphocytes, purification of antigens or indicator particles, can be estimated objectively for their value for the test system. (orig.)

324

A thermal peripheral blood flowmeter with contact force compensation  

Science.gov (United States)

This paper presents a thermal peripheral blood flowmeter where a force sensor is integrated to compensate the blood flow measurement. Since blood flow is highly sensitive to the contact force between the sensor and skin, previous blood flowmeters needed to be fixed on the skin with a constant contact force. We integrate a force sensor with a thermal blood flowmeter to measure both blood flow and contact force simultaneously for force-compensated blood flow measurement. The blood flowmeter presented here is composed of a resistance temperature detector and a piezoresistive force sensor and was fabricated by surface and bulk micromachining techniques. In the experimental measurement, the blood flow linearly decreased with the contact force at the rate of 31.7% N-1. By using the measured compensation coefficient, the device showed a constant blood flow with the maximum difference of 6.4% over the contact force variation of 1-3 N, and otherwise showed the maximum difference of 75.0%. The present device is suitable for applications with portable biomedical instrumentation or air-conditioning systems for the estimation of human thermoregulation status.

Sim, Jai Kyoung; Youn, Sechan; Cho, Young-Ho

2012-12-01

325

Circuit automatically calibrates flowmeter against liquid-level gage reference  

Science.gov (United States)

Turbine-type flowmeter uses the flow of liquid from a tank with reed-type liquid level switches as a calibration reference. A circuit to generate a reliable gate signal consists of an input and switch identification stage, monostable and bistable multivibrators, and a signal inverter and pulse output stage.

Field, R. J.

1967-01-01

326

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

327

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

328

Fluid dynamic studies on scattering aerosol and its generation for application as tracer particles in supersonic flow measurements utilizing laser Doppler velocimeter  

Science.gov (United States)

An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited oscillatory fluid velocity field and by comparing the ratio of particle velocity amplitude to the fluid velocity amplitude as a function of particle size and the frequency of oscillation. Particle velocity was measured by using a differential laser Doppler velocimeter. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. It is indicated that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

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

1974-01-01

329

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.

2013-12-01

330

A new method for filtering speckle noise in vibration signals measured by laser Doppler vibrometry for on-line quality control  

Science.gov (United States)

Mechanical fault diagnostics for quality control of manufacturing appliances is often based on the analysis of machine vibrations. In the presence of mechanical faults, vibration signals comprise periodic impulses with a characteristic frequency corresponding to a particular defect. Vibrometers based on LDV (Laser Doppler Vibrometry) are an alternative to the traditional use of piezo-electric accelerometers, devices that are the most common and popular vibration transducers. Laser vibrometry is now an established technique for vibration measurements in industrial applications where non-contact operations are essential. Despite the advantages of LDV, speckle noise occurs when rough surfaces are measured and the object is moving. Therefore, removal of speckle noise is a crucial point of a reliable system for diagnostics of mechanical faults. This paper deals with the analysis of vibration signals measured by a Laser Doppler Vibrometer from different electromechanical components such as compressors and electrical motors. The goal is to suppress the speckle-noise effect, coming both from the surface of the electro-mechanical components and its movement, in order to perform an automatic test for mechanical fault detection in the production line. First, data acquisition and its problems are introduced. Then, the chosen solution is presented. In particular, a statistical approach based on kurtosis is used for detection of speckle noise and selection of an undistorted region within the signal. The algorithm is composed of band-pass filtering, segmentation of the signal and computation of a scalar indicator KR (Kurtosis Ratio) for each signal segment, in order to detect outlying samples caused by speckle noise. Finally, real examples are shown to test the proposed method, and a tool for validation of signal databases is briefly presented.

Cristalli, Cristina; Torcianti, Barbara; Vass, Jiri

2006-06-01

331

Doppler tomography  

International Nuclear Information System (INIS)

The finding that cancer may have different Doppler characteristics from other tissues and vessels has prompted some interest in Dopper evaluation of breasts. In an effort to obtain sequences of Doppler images suitable for complete breast images, the authors have tested methods of Doppler tomography. Doppler tomography was performed in phantoms in which fluid was flowing in several tubes. The backscatter CW Doppler signal from a 2 MHz carrier was measured for 128 samples along 200 profiles taken at equispaced angles of view around the phantom. The RF signal was mixed to base stand, low pass filtered, and A/D converted to 10 KHz for subsequent computer analysis. The Doppler power in a specified frequency band was used to eliminate number of particles moving within a certain velocity range. Reconstructed images were obtained with and without flow in tubes within excised human breast. Images proportional to number of particles flowing at velocities greater than a certain velocity were of good quality. The results show that Dopper tomography is a distinct possibility even though the vector nature of Doppler shift causes some inconsistencies in the data

332

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

333

Experimental Research of Crosscorrelation-Based Virtual Dynamic Flowmeter  

International Nuclear Information System (INIS)

An innovated method for measuring dynamic flow is put forward, and a virtual dynamic flowmeter is established. Basing on the principle of pressure pulse containing the flow information, for the dynamic laminar flow, by means of collecting the pressure signals at two points at interval of L and processing them with crosscorrelation calculation, then the transit time is gained, consequently the average flow rate can be got. This calculation is prosecuted repeatedly according to a certain time step length, thus the average flow rates in each time slice can be acquired. If the step length is decreased to zero, the piecewise average flow rate is approximate to the instant dynamic flow. In order to calibrate the virtual dynamic flowmeter, the unloaded servo cylinder was used for the contrasting experiment. The accuracy and validity of this approach has been proved

334

Concentration measurement systems with stable solutions for binary gas mixtures using two flowmeters  

International Nuclear Information System (INIS)

The previously proposed gas concentration measurement system (Yamazaki et al 2007 Meas. Sci. Technol. 18 2762–8) shows a considerable error for some combinations of gases. The error increases when the system of equations determining mole fractions becomes a mathematically ill-conditioned system. Because the parameters of the equations reflect the material properties of the gases, the current paper considers flowmeters whose flow rate indication does not involve any gas property. This paper firstly illustrates the ill condition for the combination of venturi meter and laminar flowmeters. The paper then discusses the simultaneous measurement of flow rate and mole fractions by flowmeter combinations: an ultrasonic flowmeter and a venturi meter, an ultrasonic flowmeter and a laminar flowmeter. Experiments are conducted for a mixture of argon and air. When a venturi meter and a laminar flowmeter are used, the equations to evaluate the gas mixture ratio become an ill-conditioned system, and hence the evaluated mixture ratio shows a considerable error. On the other hand, the combination of an ultrasonic flowmeter and a laminar flowmeter detects the gas mixture ratio with proper accuracy

335

Flowmeters for use in the nuclear industry: How to select the appropriate instrument  

International Nuclear Information System (INIS)

Because flow is one of the most common process variables measured, numerous types of flowmeters based on a variety of measurement principles are available. Although these numerous flowmeter types allow one to measure almost any flow, the wide variety also makes selecting an appropriate flowmeter a complex and potentially difficult task. This paper reviews the definition and importance of basic hydraulic principles and the design parameters critical to an accurate flow measurement, the principles used in flow monitoring and their advantages and disadvantages, and a method for selecting an appropriate flowmeter. 6 refs

336

The wide-range ejector flowmeter: calibrated gas evacuation comprising both high and low gas flows.  

Science.gov (United States)

The wide-range ejector flowmeter is an active scavenging system applying calibrated gas removal directly to the anaesthetic circuit. The evacuation rate can be adjusted on the flowmeter under visual control using the calibration scale ranging from 200 ml X min-1 to 151 X min-1. The accuracy of the calibration was tested on three ejector flowmeters at 12 different presettings. The percentage deviation from presetting varied from + 18 to - 19.4 per cent. The ejector flowmeter enables the provision of consistent and accurately calibrated extraction of waste gases and is applicable within a wide range of fresh gas flows. PMID:6238660

Waaben, J; Brinkløv, M M; Jørgensen, S

1984-11-01

337

In-plant calibration of magnetic flowmeters in the pulp and paper industries  

International Nuclear Information System (INIS)

A number of magnetic flowmeters for pulp flow measurements were calibrated by means of the tracer velocity method during working conditions. Some of the meters were calibrated regularly during a period of more than 2 yr. The deviations between tracer measurements and flowmeter readings varied from -20% to + 30%. Some possible sources of error are discussed. The results clearly show the necessity of in-plant calibrations of magnetic flowmeters when accurate flow values are needed, which is usually the case when expensive flowmeters like the magnetic ones are used. (author)

338

Calibration of a miniature permanent magnet flowmeter probe for velocity and temperature measurement in sodium  

International Nuclear Information System (INIS)

For the calibration of a miniature permanent magnet flowmeter probe, the working principle of which is based on the induction law, a measuring specification is given which allows to determine reproducibly the sensitivity of the flowmeter probe and the zero offsets of the temperature compensated voltages. The flowmeter probe has an outer diameter of 2.5 mm and is equipped with three-wire-thermocouples (Alumel/Chromel/stainless steel). The K- and S-values which are characteristic of the flowmeter probe are determined and discussed. (orig.)

339

Rotor Re-Design for the SSME Fuel Flowmeter  

Science.gov (United States)

The present report describes the process of redesigning a new rotor for the SSME Fuel Flowmeter. The new design addresses the specific requirement of a lower rotor speed which would allow the SSME operation at 1 15% rated power level without reaching a blade excitation by the wakes behind the hexagonal flow straightener upstream at frequencies close to the blade natural frequency. A series of calculations combining fleet flowmeters test data, airfoil fluid dynamics and CFD simulations of flow patterns behind the flowmeter's hexagonal straightener has led to a blade twist design alpha = alpha (radius) targeting a kf constant of 0.8256. The kf constant relates the fuel volume flow to the flowmeter rotor speed, for this particular value 17685 GPM at 3650 RPM. Based on this angle distribution, two actual blade designs were developed. A first design using the same blade airfoil as the original design targeted the new kf value only. A second design using a variable blade chord length and airfoil relative thickness targeted simultaneously the new kf value and an optimum blade design destined to provide smooth and stable operation and a significant increase in the blade natural frequency associated with the first bending mode, such that a comfortable margin could be obtained at 115% RPL. The second design is a result of a concurrent engineering process, during which several iterations were made in order to achieve a targeted blade natural frequency associated with the first bending mode of 1300 Hz. Water flow tests preliminary results indicate a kf value of 0.8179 for the f-irst design, which is within 1% of the target value. The second design rotor shows a natural frequency associated with the first bending mode of 1308 Hz, and a water-flow calibration constant of kf 0.8169.

Marcu, Bogdan

1999-01-01

340

Pengukuran Aliran Steam Menggunakan Head Flowmeter Dengan Differensial Pressure Transmitter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pengukuran aliran steam sangatlah penting untuk mengetahui jumlah steam yang mengalir selama proses berlangsung serta pengukuran aliran steam ini juga berguna untuk mengatur jalannya proses sehingga dapat meningkatkan hasil produksi agar tetap stabil. Head Flowmeter dengan Differensial Pressure Transmitter (D/P Transmitter) adalah salah satu peralatan pengukur aliran fluida maupun steam yang dipergunakan untuk mengukur besarnya jumlah fluida yang mengalir dalam pipa dan D/P Transmitter ber...

Prabudi, Agus

2010-01-01

 
 
 
 
341

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

342

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

State-of-the-art Doppler experiments require wavelength calibration with precision at the cm/s level. A low-finesse Fabry-Perot interferometer (FPI) can provide a wavelength comb with a very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling the FPI cavity, we propose to passively stabilize the interferometer and track the time-dependent cavity length drift externally. A dual-fin...

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

2014-01-01

343

Simultaneous sub-Doppler laser cooling of fermionic $^6$Li and $^{40}$K on the D$_1$ line: Theory and Experiment  

CERN Document Server

We report on simultaneous sub-Doppler laser cooling of fermionic $^6$Li and $^{40}$K using the D$_1$ optical transitions. We compare experimental results to a numerical simulation of the cooling process applying a semi-classical Monte Carlo wavefunction method. The simulation takes into account the three dimensional optical molasses setup and the dipole interaction between atoms and the bichromatic light field driving the D$_1$ transitions. We discuss the physical mechanisms at play, we identify the important role of coherences between the ground state hyperfine levels and compare D$_1$ and D$_2$ sub-Doppler cooling. In 5 ms, the D$_1$ molasses phase largely reduces the temperature for both $^6$Li and $^{40}$K at the same time, with a final temperature of 44 $\\mu$K and 11 $\\mu$K, respectively. For both species this leads to a phase-space density close to $10^{-4}$. These conditions are well suited to directly load an optical or magnetic trap for efficient evaporative cooling to quantum degeneracy.

Sievers, Franz; Kretzschmar, Norman; Fernandes, Diogo Rio; Suchet, Daniel; Rabinovic, Michael; Parker, Colin V; Khaykovich, Lev; Salomon, Christophe; Chevy, Frédéric

2014-01-01

344

Wavelet series method for reconstruction and spectral estimation of laser Doppler velocimetry data. An application to a screeching rectangular jet LDV measurements  

Energy Technology Data Exchange (ETDEWEB)

Many techniques have been developed in order to obtain spectral density function from randomly sampled data, such as the computation of a slotted autocovariance function. Nevertheless, one may be interested in obtaining more information from laser Doppler signals than a spectral content, using more or less complex computations that can be easily conducted with an evenly sampled signal. That is the reason why reconstructing an evenly sampled signal from the original LDV data is of interest. The ability of a wavelet-based technique to reconstruct the signal with respect to statistical properties of the original one is explored, and spectral content of the reconstructed signal is given and compared with estimated spectral density function obtained through classical slotting technique. Furthermore, LDV signals taken from a screeching jet are reconstructed in order to perform spectral and bispectral analysis, showing the ability of the technique in recovering accurate information's with only few LDV samples. (orig.)

Jaunet, Vincent; Collin, Erwan; Bonnet, Jean-Paul [CEAT, PPRIME Institute, UPR 3346, Poitiers Cedex (France)

2012-01-15

345

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

346

Comparison of magnetic resonance imaging and Laser Doppler Anemometry velocity measurements downstream of replacement heart valves : implications for in vivo assessment of prosthetic valve function  

DEFF Research Database (Denmark)

The non-invasive, in-vivo assessment of prosthetic valve function is compromised by the lack of accurate measurements of the transvalvular flow fields or hemodynamics by current techniques. Short echo time magnetic resonance imaging (MRI) may provide a method for the non-invasive, in vivo assessment of prosthetic valve function by accurately measuring changes in the transvalvular flow fields associated with normal and dysfunctional prosthetic valves. The objectives of these in vitro experiments were to investigate the potential for using MRI as a tool to measure the complex flow fields distal to replacement heart valves, and to assess the accuracy of MRI velocity measurements by comparison with Laser Doppler Anemometry (LDA), a gold standard.

Fontaine, A A; Heinrich, R S

1996-01-01

347

Doppler-Free Spectroscopy of the 1S0-3P0 Optical Clock Transition in Laser-Cooled Fermionic Isotopes of Neutral Mercury  

International Nuclear Information System (INIS)

We report direct laser spectroscopy of the 1S0-3P0 transition at 265.6 nm in fermionic isotopes of neutral mercury in a magneto-optical trap. Measurements of the frequency against the LNE-SYRTE primary reference using an optical frequency comb yield 1 128 575 290 808.4±5.6 kHz in 199Hg and 1 128 569 561 139.6±5.3 kHz in 201Hg. The uncertainty, allowed by the observation of the Doppler-free recoil doublet, is 4 orders of magnitude lower than previous indirect determinations. Mercury is a promising candidate for future optical lattice clocks due to its low sensitivity to blackbody radiation

348

Evaluation of late radiation-induced changes of the superficial microcirculation after acute ?-irradiation. II. prognostic importance of the cutaneous doppler laser  

International Nuclear Information System (INIS)

Objective. -The changes that occur in the tissular microcirculation after accidental acute irradiation account for some of the early effects of such irradiation, especially at the cutaneous level. The prognostic importance of the cutaneous laser doppler was tested in an experimental model of acute ?-irradiation. Methods.-Ten pigs were given ?-irradiation with a high single localized dose of 90Sr/90Y (32 or 64 Gy, 7 mg/cm2) delivered to the flank, and were evaluated 2, 7, 14, 21 and 28 days thereafter. Each individual was its own control. The local microcirculation was measured in the resting state and during thermal stimulation at 42 deg. C, using a Periflux cutaneous Doppler laser with p413 probes. Three periods of six minutes each were continuously recorded: period 1 (P1) represented basal resting cutaneous perfusion, with the slope p corresponding to the increase in perfusion when two minutes of thermal stimulation at 42 deg. C began; P2 to plateau perfusion during this stimulation; and P3 to perfusion on the return to equilibrium. Results. -After acute ?-irradiation in the pig, all the cutaneous microcirculation parameters measured (P1, p, P2 and P3) had risen at day 2 in the irradiated area by a factor of 2 to 4, depending on the dose (p < 0.001), compared to the adjacent control area. On the other hand, as from day 7, the resting and the stimulated microcirculation varied little, except for a reduction of the slope p by a factor a reduction of the slope p by a factor of 2 (p < 0.05) after the strongest radiation dose. Conclusion. -After acute irradiation, the increase in the resting cutaneous microcirculation may correspond to immediate but transitory capillary vasodilatation that accompanies the initial erythema in accidental irradiation. The absence of vascular response to thermal stimulation seems to be a good means of reaching an early diagnosis of delayed cutaneous radiation necrosis. (authors)

349

Laser-induced line-narrowing effects in coupled Doppler-broadened transitions. II - Standing-wave features.  

Science.gov (United States)

Previous theoretical results on the influence of a laser on the line shape of a coupled transition (laser-induced line narrowing) have been restricted to the case where the laser is detuned from the center of its atomic gain profile or is in the form of a traveling wave. The present paper extends these results to the case where the laser is an intense standing-wave field tunable to the center of its atomic gain profile (conditions for Lamb dip). A theoretical solution of the problem is developed, and a detailed discussion of line shapes and physical processes involved is included.

Feldman, B. J.; Feld, M. S.

1972-01-01

350

Practical experience of using thermal-mass flowmeters at the registration associated (free) petroleum gas  

Science.gov (United States)

The results of field tests of thermal-mass flowmeter TurboFlow TFG-S in comparison with ultrasonic flowmeter Dymetic-1223K at existing oil and gas extraction object are given in the article. Measured medium – associated (free) petroleum gas.

Fazlyyyakhmatov, M. G.; Kashapov, N. F.; Khayritonov, Kh A.; Lazarev, D. K.; Lazarev, V. K.

2014-12-01

351

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.)

352

Development of a wide range vortex shedding flowmeter for high temperature helium gas  

International Nuclear Information System (INIS)

A flowmeter was required to measure recirculating helium gas flow over a wide range of conditions in a gas-cooled fast reactor (GCFR) core flow simulator, the ORNL Core Flow Test Loop (CFTL). The flow measurement requirements of the CFTL exceeded the proven performance of any single conventional flowmeter. Therefore, a special purpose vortex shedding flowmeter (VSFM) was developed. A single flowmeter capable of meeting all the CFTL requirements would provide significant economic and performance advantages in the operation of the loop. The development, conceptual design, and final design of a modified VSFM are described. The results of extensive flow calibration of the flowmeter at the Colorado Engineering Experiment Station (CEES) are presented. The report closes with recommendations for application of the VSFM to the CFTL and for future development work

353

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 16N 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 16N 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 operatio 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)

354

Skew photonic Doppler velocimetry to investigate the expansion of a cloud of droplets created by micro-spalling of laser shock-melted metal foils  

Energy Technology Data Exchange (ETDEWEB)

Dynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied sciences. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. Major difficulties arise from the loss of free surface reflectivity at shock breakout and from the wide distribution of particle velocities within this cloud. We present laser shock experiments on tin and aluminium, to pressures ranging from about 70 to 160 GPa, with complementary diagnostics including a photonic Doppler velocimeter set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta. The records are roughly consistent with a one-dimensional theoretical description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. The main discrepancies between measured and calculated velocity profiles are discussed in terms of edge effects evidenced by transverse shadowgraphy.

Loison, D.; Resseguier, T. de; Dragon, A. [Institut P' , UPR 3346, CNRS, Universite de Poitiers, ISAE-ENSMA - 1, av Clement Ader, 86961 Futuroscope (France); Mercier, P.; Benier, J.; Deloison, G.; Lescoute, E.; Sollier, A. [CEA, DAM, DIF - 91297 Arpajon (France)

2012-12-01

355

Skew photonic Doppler velocimetry to investigate the expansion of a cloud of droplets created by micro-spalling of laser shock-melted metal foils  

International Nuclear Information System (INIS)

Dynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied sciences. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. Major difficulties arise from the loss of free surface reflectivity at shock breakout and from the wide distribution of particle velocities within this cloud. We present laser shock experiments on tin and aluminium, to pressures ranging from about 70 to 160 GPa, with complementary diagnostics including a photonic Doppler velocimeter set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta. The records are roughly consistent with a one-dimensional theoretical description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. The main discrepancies between measured and calculated velocity profiles are discussed in terms of edge effects evidenced by transverse shadowgraphy.

356

On the Traceability of Accuracy of Ultrasonic Flowmeter  

International Nuclear Information System (INIS)

Time-of-flight ultrasonic flowmeters have been widely used these days in industry. It is however in suspicion if its high accuracy is traceable to the national standard. It was made clear why traceability cannot be guaranteed from a fluid mechanical point of view. The main reason is a difference of flow configuration between the flow standard and the measurement position on-site. The concept of 'Facility Factor' is introduced and it is concluded that the 'Profile Factor' is not sufficient for correcting the meter reading. It is discussed that measurement of velocity profile on-site is essentially required. (author)

357

Samarium-cobalt magnets for flowmeters in steam generators  

International Nuclear Information System (INIS)

Investigations on microstructure of magnetic and service properties of cast permanent magnets, made of Sm-Co-Cu-Fe and Ce-Sm-Co-Cu-Fe system alloys, are carried out. It is shown that annealing at 1000 deg C and further ageing at 450 deg C promotes the formation of fine dispersed structure, conditioning the high-coercive state of the alloy. tests of magnets under operation conditions (water at 205 deg C and 70 kgs/cm2) demonstrated stable work during the whole service period of flowmeters of steam-generators

358

Output-only Modal Analysis using Continuous-Scan Laser Doppler Vibrometry and application to a 20 kW wind turbine  

Science.gov (United States)

Continuous-Scan Laser Doppler Vibrometry (CSLDV) is a technique where the measurement point continuously sweeps over a structure while measuring, capturing both spatial and temporal information. The continuous-scan approach can greatly accelerate measurements, allowing one to capture spatially detailed mode shapes in the same amount of time that conventional methods require to measure the response at a single point. The method is especially beneficial when testing large structures, such as wind turbines, that have low natural frequencies and hence may require very long time records at each measurement point. Several CSLDV methods have been presented that use sinusoidal excitation or impulse excitation, but CSLDV has not previously been employed with an unmeasured, broadband random input. This work extends CSLDV to that class of input, developing an Output-only Modal Analysis method (OMA-CSLDV). A recently developed algorithm for linear time-periodic system identification, which makes use of harmonic power spectra and the harmonic transfer function concept developed by Wereley [17], is used in conjunction with CSLDV measurements. One key consideration, the choice of the scan frequency, is explored. The proposed method is validated on a randomly excited free-free beam, where one-dimensional mode shapes are captured by scanning the laser along the length of the beam. The first seven natural frequencies and mode shapes are extracted from the harmonic power spectrum of the vibrometer signal and show good agreement with the analytically-derived modes of the beam. The method is then applied to identify the mode shapes of a parked 20 kW wind turbine using a ground based laser and with only a light breeze providing excitation.

Yang, Shifei; Allen, Matthew S.

2012-08-01

359

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

International Nuclear Information System (INIS)

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 ?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

360

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 in Turkey and measurement results are given. Experimental results proved that the values measured by the electromagnetic flowmeter (EMF are affected by cathodic protection system current. Comments on the measurement results are made and precautions to be taken are proposed.

Ozge Sahin

2007-01-01

 
 
 
 
361

Left coronary arterial blood flow: Noninvasive detection by Doppler US  

International Nuclear Information System (INIS)

Continuous wave (CW) and pulsed Doppler ultrasound studies with spectral analysis were used to detect the left coronary arterial blood flow in patients who were undergoing routine echocardiography. The pulmonary artery is a stable ultrasonic landmark from which detection of the blood flow can be effected. The left coronary artery can be distinguished by its blood flow toward the cardiac apex and by specific, functional flow features. Flow patterns vary among the left main, circumflex, and anterior descending arteries; patterns also vary with respiration cycles. In the present study, coronary arterial blood flow was detected in 58 of 70 patients (83%). Findings were validated by selectively injecting an agitated saline contrast medium into the left coronary artery and, in another study, by comparing human Doppler phasic flow waveforms with electromagnetic flowmeter recordings obtained in dogs

362

Two-point laser Doppler velocimetry measurements in a Mach 1.2 cold supersonic jet for statistical aeroacoustic source model  

Energy Technology Data Exchange (ETDEWEB)

Single and multi-point laser Doppler velocimetry measurements performed in a cold Mach 1.2 jet flow are used to assess those properties of the aerodynamic field most relevant in the generation of turbulence mixing noise. Single point measurements yield mean velocity profiles, turbulence intensity profiles and power spectral densities of both the velocity and Reynolds stress fields at seven axial stations between the jet exit and the end of the potential core. The longitudinal components of the second-order and fourth-order two-point velocity correlation tensor are obtained from a series of multi-point LDV measurements, whence a cartography of integral space and time scales, convection velocities and acoustic compactness is effected. These results are used to examine differences between subsonic and supersonic jet aerodynamics in terms of their sound generating potential. Finally analytical expressions are proposed for the spatial and temporal parts of the longitudinal correlation coefficient function. These are scaled using the integral space and time scales of the velocity and Reynolds stress fields, and excellent agreement is found with experimentally determined functions. (orig.)

Kerherve, F.; Jordan, P.; Gervais, Y.; Valiere, J.C.; Braud, P. [Laboratoire d' Etudes Aerodynamiques, Batiment K, UMR Centre National de la Recherche Scientifique 6609, 40 Avenue du Recteur Pineau, 86000, Poitiers (France)

2004-09-01

363

Laser-Doppler imaging of activation-flow coupling in the somatosensory cortex: normalization of signal when the baseline changes significantly.  

Science.gov (United States)

This study describes two approaches used to normalize the laser-Doppler flowmetry (LDF) signal, corresponding to the regional cerebral blood flow (rCBF) response after electrical hind-paw stimulation. The first approach divides the LDF signal to the baseline and subsequently integrates the response curve from the rise point to the termination point (defined formally as "normalized rCBF response", and the second subtracts the baseline from the LDF signal and subsequently integrates the response curve from the rise point to the termination point (defined as "absolute rCBF response"). Both parameters are given in arbitrary units. A comparative analysis of the changes in the "normalized" and "absolute" LDrCBF response is presented both for when the baseline does not change significantly, and for when the baseline changes significantly under the influence of different factors. In summary, when the baseline changes significantly it is preferable to normalize the LDrCBF response towards the baseline by subtraction, not by division. PMID:12616701

Zhelev, Z; Bakalova, R

2002-11-01

364

Monitoring hypoxia induced changes in cochlear blood flow and hemoglobin concentration using a combined dual-wavelength laser speckle contrast imaging and Doppler optical microangiography system.  

Science.gov (United States)

A synchronized dual-wavelength laser speckle contrast imaging (DWLSCI) system and a Doppler optical microangiography (DOMAG) system was developed to determine several ischemic parameters in the cochlea due to a systemic hypoxic challenge. DWLSCI can obtain two-dimensional data, and was used to determine the relative changes in cochlear blood flow, and change in the concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (Hb) and total hemoglobin (HbT) in mice. DOMAG can obtain three-dimensional data, and was used to determine the changes in cochlear blood flow with single vessel resolution. It was demonstrated that during a hypoxic challenge there was an increase in the concentrations of Hb, a decrease in the concentrations of HbO and cochlear blood flow, and a slight decrease in the concentration of HbT. Also, the rate of change in the concentrations of Hb and HbO was quantified during and after the hypoxic challenge. The ability to simultaneously measure these ischemic parameters with high spatio-temporal resolution will allow the detailed quantitative analysis of several hearing disorders, and will be useful for diagnosing and developing treatments. PMID:23272205

Reif, Roberto; Qin, Jia; Shi, Lei; Dziennis, Suzan; Zhi, Zhongwei; Nuttall, Alfred L; Wang, Ruikang K

2012-01-01

365

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)

366

Comparison of neovascularization in dermal substitutes seeded with autologous fibroblasts or impregnated with bFGF applied to diabetic foot ulcers using laser Doppler imaging.  

Science.gov (United States)

A bilayered artificial dermis (AD) composed of an upper silicone sheet and a lower collagen sponge has been widely applied for skin defects. After application, fibroblasts and capillaries infiltrate the AD and the collagen sponge is replaced by host dermal tissue within a few weeks. However, this delay and the high incidence of infection are concerns regarding the use of AD in the treatment of chronic ulcers. In this study, we compared the neovascularization of conventional AD seeded with autologous fibroblasts (cultured dermis: CD) and collagen/gelatin sponge (CGS), which is a novel artificial dermis capable of sustained release of basic fibroblast growth factor (bFGF) after application using laser Doppler imaging (LDI). CD (n = 5) and CGS impregnated with bFGF (n = 6) were applied to diabetic foot ulcers after debridement. Perfusion units (PUs) were measured just after, and 1, 2 and 3 weeks after application, and complete healing rates within 16 weeks were compared. No significant differences in PUs were seen 1, 2 and 3 weeks after application and in healing rates within 16 weeks between the two groups. This study suggested that CD and CGS treatments were effective, but there were no significant differences between them in the treatment of diabetic ulcers . PMID:25028148

Morimoto, Naoki; Kakudo, Natsuko; Valentin Notodihardjo, Priscilla; Suzuki, Shigehiko; Kusumoto, Kenji

2014-12-01

367

Performance assessment of a blind test using the University of Mississippi's acoustic/seismic laser Doppler vibrometer (LDV) mine detection apparatus at Fort A. P. Hill  

Science.gov (United States)

In March of 1999, a research team from the University of Mississippi brought its data acquisition system consisting of an acoustic/seismic laser Doppler vibrometer (LDV) mine detection sensor, to Fort A P Hill in Virginia. The purpose was to collect data over a variety of miens and to participate in a blind test. IN the blind test, the mine detection apparatus was brought to several 1-m by 1-m areas included a mix of mines, blank spots., and clutter spots as determined from prior test. The data collected over each of these spots was visualized in real time, an a mine/no mine decision was made. The resultant probability of detection was 95 percent with a false-alarm rate (FAR) of 0.03 m-3. We present a description of the test and a detailed analysis of the data collected by the University of Mississippi in the mine lanes at AP Hill. With knowledge of the baseline, we compute target and clutter statistics, including signal-to-clutter ratios for various categories of mine types and mine depths. We examine detection trends as a function of frequency. Applying image-processing techniques to the data, features such as size and shape are extracted, and the resultant feature-level target and clutter histograms are used to improve performance. The expected performance with a without feature is compared to the demonstrated performance.

Rosen, Erik M.; Sherbondy, Kelly D.; Sabatier, James M.

2000-08-01

368

Fisher information and Shannon entropy for on-line detection of transient signal high-values in laser Doppler flowmetry signals of healthy subjects  

International Nuclear Information System (INIS)

Laser Doppler flowmetry (LDF) is an easy-to-use method for the assessment of microcirculatory blood flow in tissues. However, LDF recordings very often present TRAnsient Signal High-values (TRASH), generally of a few seconds. These TRASH can come from tissue motions, optical fibre movements, movements of the probe head relative to the tissue, etc. They often lead to difficulties in signal global interpretations. In order to test the possibility of detecting automatically these TRASH for their removal, we process noisy and noiseless LDF signals with two indices from information theory, namely Fisher information and Shannon entropy. For this purpose, LDF signals from 13 healthy subjects are recorded at rest, during vascular occlusion of 3 min, and during post-occlusive hyperaemia. Computation of Fisher information and Shannon entropy values shows that, when calibrated, these two indices can be complementary to detect TRASH and be insensitive to the rapid increases of blood flow induced by post-occlusive hyperaemia. Moreover, the real-time algorithm has the advantage of being easy to implement and does not require any frequency analysis. This study opens new fields of application for Fisher information and Shannon entropy: LDF 'denoising'

369

Simulations and Measurements of Human Middle Ear Vibrations Using Multi-Body Systems and Laser-Doppler Vibrometry with the Floating Mass Transducer  

Directory of Open Access Journals (Sweden)

Full Text Available The transfer characteristic of the human middle ear with an applied middle ear implant (floating mass transducer is examined computationally with a Multi-body System approach and compared with experimental results. For this purpose, the geometry of the middle ear was reconstructed from ?-computer tomography slice data and prepared for a Multi-body System simulation. The transfer function of the floating mass transducer, which is the ratio of the input voltage and the generated force, is derived based on a physical context. The numerical results obtained with the Multi-body System approach are compared with experimental results by Laser Doppler measurements of the stapes footplate velocities of five different specimens. Although slightly differing anatomical structures were used for the calculation and the measurement, a high correspondence with respect to the course of stapes footplate displacement along the frequency was found. Notably, a notch at frequencies just below 1 kHz occurred. Additionally, phase courses of stapes footplate displacements were determined computationally if possible and compared with experimental results. The examinations were undertaken to quantify stapes footplate displacements in the clinical practice of middle ear implants and, also, to develop fitting strategies on a physical basis for hearing impaired patients aided with middle ear implants.

Tobias Strenger

2013-10-01

370

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

371

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  

International Nuclear Information System (INIS)

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

372

Comparison between Hilbert-Huang transform and scalogram methods on non-stationary biomedical signals: application to laser Doppler flowmetry recordings  

International Nuclear Information System (INIS)

A significant transient increase in laser Doppler flowmetry (LDF) signals is observed in response to a local and progressive cutaneous pressure application on healthy subjects. This reflex may be impaired in diabetic patients. The work presents a comparison between two signal processing methods that provide a clarification of this phenomenon. Analyses by the scalogram and the Hilbert-Huang transform (HHT) 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 at different time intervals in order to take into account the dynamics of the phenomenon. The results show that both the scalogram and the HHT methods lead to the same conclusions concerning the comparisons of the myogenic, neurogenic and endothelial related metabolic activities-during the progressive pressure and at rest-in healthy and diabetic subjects. However, the HHT shows more details that may be obscured by the scalogram. Indeed, the non-locally adaptative limitations of the scalogram can remove some definition from the data. These results may improve knowledge on the above-mentioned reflex as well as on non-stationary biomedical signal processing methods

373

Differences in the beat-to-beat parameters of skin-surface pulsatile laser-Doppler waveforms between stroke and normal subjects.  

Science.gov (United States)

Walking can help improve the recovery after stroke. The present study used skin-surface laser-Doppler flowmetry (LDF) measurements and beat-to-beat waveform analysis with the aim of discriminating the microcirculatory blood flow (MBF) characteristics in stroke subjects subdivided into two groups according to their walking ability. Five-minute LDF measurements were performed in the following groups: Group A (cannot walk independently; n = 17), Group B (can walk independently; n = 11), and Group C (healthy controls; n = 17). The pulse width (PW) and foot delay time (FDT) and their coefficients of variation (PWCV and FDTCV, respectively) were calculated for the beat-to-beat LDF waveform. The FDT in Group A and the blood-pressure-normalized PW in Group C were significantly longer than the corresponding values in the other groups, and PWCV and FDTCV were significantly larger in Group C than in Group A. To our knowledge this is the first study demonstrating the feasibility of using a beat-to-beat LDF waveform index to discriminate between stroke subjects with different walking abilities and between stroke and normal subjects. It provides a noninvasive and real-time method for discriminating MBF characteristics, and thus could aid the development of an index for the early detection of stroke or for evaluating the recovery condition in stroke patients. PMID:23370158

Hsiu, Hsin; Huang, Shih-Min; Chen, Chao-Tsung; Hsu, Wei-Chen; Lin, Fong-Cheng

2014-01-01

374

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...

Ozge Sahin; Serdar Gundogdu

2007-01-01

375

API testing program - calibration of microprocessor based flowmeters for integrated metering systems  

Energy Technology Data Exchange (ETDEWEB)

Microprocessor based flowmeter technologies for liquids, such as Coriolis mass meters, and Ultrasonic flowmeters hold great promise. These technologies offer many advantages, such as no rotating parts, self-diagnostic checks, which can help anticipate and warn of impending failures before they have a major impact on the measurement. These meters are substantially different though than other primary devices due to their heavy reliance on the accompanying secondary electronics. One method to prove that they are accurate would be proving the flowmeter, using a pipe prover or small volume prover (SVP), but these proving methods are designed to count 'real time' pulses from a turbine or PD meter between a known volume, they are not designed to count 'time delayed' 'manufactured pulses' from a microprocessor. There are limitations of the manufactured pulse train and it affects the ability of the flowmeter to be proved using current proving technology. The author of this paper, a chairman of an American Petroleum Institute working group, investigated how the 'microprocessor generated pulses' produced by these types of flowmeters, interacted with the existing measurement technologies in use today. Several microprocessor based flowmeter technologies have been tested, including; Ultrasonic, Coriolis, and Helical Turbine with pulse multiplying preamplifier. Wherever possible, flowmeters of various sizes, and from several vendors have been tested. A significant amount of data has been collected which sheds light into why these types of flowmeters are sometimes difficult to prove. This paper describes the API testing program, and the methodology behind it. It presents results and findings, and offers specific recommendations that may eventually be incorporated into API documents and/or standards in the future. (author)

Elliot, Kenneth D. [Omni Flow Computers, Inc., Stafford, TX (United States)

2005-07-01

376

Guided wave-based J-integral estimation for dynamic stress intensity factors using 3D scanning laser Doppler vibrometry  

Science.gov (United States)

The application of guided waves to interrogate remote areas of structural components has been researched extensively in characterizing damage. However, there exists a sparsity of work in using piezoelectric transducer-generated guided waves as a method of assessing stress intensity factors (SIF). This quantitative information enables accurate estimation of the remaining life of metallic structures exhibiting cracks, such as military and commercial transport vehicles. The proposed full wavefield approach, based on 3D laser vibrometry and piezoelectric transducer-generated guided waves, provides a practical means for estimation of dynamic stress intensity factors (DSIF) through local strain energy mapping via the J-integral. Strain energies and traction vectors can be conveniently estimated from wavefield data recorded using 3D laser vibrometry, through interpolation and subsequent spatial differentiation of the response field. Upon estimation of the Jintegral, it is possible to obtain the corresponding DSIF terms. For this study, the experimental test matrix consists of aluminum plates with manufactured defects representing canonical elliptical crack geometries under uniaxial tension that are excited by surface mounted piezoelectric actuators. The defects' major to minor axes ratios vary from unity to approximately 133. Finite element simulations are compared to experimental results and the relative magnitudes of the J-integrals are examined.

Ayers, J.; Owens, C. T.; Liu, K. C.; Swenson, E.; Ghoshal, A.; Weiss, V.

2013-01-01

377

??????????? ?????? ??? ????????? ??? ????????? ??? ????????????? laser ?? ???????  

Digital Repository Infrastructure Vision for European Research (DRIVER)

1)?????? ???????????? ??? ???????????? ?????????? ????????? ??? ????????? ??? ????????????? laser ?? ?????? ??????? ?? ???????????? ????? ??? ?? ????????. 2)?????? ???????? ???????????? ?? ??? ?????? LIBS ?? ??? ??????? ??????????????? ????????? ??????? ???????? ??? ?????...

????????, ??????

2007-01-01

378

Near-UV sub-Doppler spectroscopy on a metastable Mg beam by a frequency-doubled diode laser  

International Nuclear Information System (INIS)

Near-UV radiation is generated by doubling the frequency of a semiconductor laser in a nonlinear crystal. The crystal is contained in a resonant cavity in order to improve the conversion efficiency. The cavity increases the efficiency by about three orders of magnitude. This radiation has been used to perform spectroscopy of metastable magnesium in an atomic beam. We observed the (3s3p)3P-(3s3d)3D transition multiplet, which is of interest for metrological applications. The isotopic shift between 24Mg and 26Mg was measured and new information on the hyperfine structure of 25Mg was obtained. This radiation source is promising also in order to improve the Mg frequency standard. (orig.)

379

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 irea, 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

380

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

 
 
 
 
381

Borehole Flowmeter Logging for the Accurate Design and Analysis of Tracer Tests.  

Science.gov (United States)

Tracer tests often give ambiguous interpretations that may be due to the erroneous location of sampling points and/or the lack of flow rate measurements through the sampler. To obtain more reliable tracer test results, we propose a methodology that optimizes the design and analysis of tracer tests in a cross borehole mode by using vertical borehole flow rate measurements. Experiments using this approach, herein defined as the Bh-flow tracer test, have been performed by implementing three sequential steps: (1) single-hole flowmeter test, (2) cross-hole flowmeter test, and (3) tracer test. At the experimental site, core logging, pumping tests, and static water-level measurements were previously carried out to determine stratigraphy, fracture characteristics, and bulk hydraulic conductivity. Single-hole flowmeter testing makes it possible to detect the presence of vertical flows as well as inflow and outflow zones, whereas cross-hole flowmeter testing detects the presence of connections along sets of flow conduits or discontinuities intercepted by boreholes. Finally, the specific pathways and rates of groundwater flow through selected flowpaths are determined by tracer testing. We conclude that the combined use of single and cross-borehole flowmeter tests is fundamental to the formulation of the tracer test strategy and interpretation of the tracer test results. PMID:25417730

Basiricò, Stefano; Crosta, Giovanni B; Frattini, Paolo; Villa, Alberto; Godio, Alberto

2014-11-21

382

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 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

383

Characteristics of multipath ultrasonic flowmeter installed upstream and downstream of flow disturbance factors-Contraction, Expansion, and Tee Pipe  

International Nuclear Information System (INIS)

Multipath ultrasonic flowmeters are increasingly being used for the purpose of accurate flow measurement. However, an installation standard has not yet been established for these flowmeters, and this can cause considerable confusion during field installation. There is a need for a minimum straight run to ensure the measurement accuracy of a flowmeter installed upstream and downstream of flow disturbance factors expansion, contraction, and tee pipes. Experiments were performed by using multipath flowmeters that have less than ±0.5% accuracy 4 paths 1 unit and 2 paths 1 unit are of foreign make, whereas 5 paths 2 units are of domestic make to determine the straight run under the above conditions. We carried out experiments repeatedly by considering a straight run, velocity, and suggested installation standards for a multipath ultrasonic flowmeter that satisfies the tolerance limits

384

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

385

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

386

A test circuit for calibration of liquid and supercritical helium flowmeters  

International Nuclear Information System (INIS)

This chapter investigates the behavior of flow transducers in different pressure conditions using a closed loop in which each component can withstand pressures up to 3 MPa. The test circuit consists of a variable speed superconducting motor, a centrifugal pump, a multi-function valve and a test section. It includes a commercial turbine transducer used as a reference standard flowmeter. An absolute calibration system, built for calibrating the turbine flowmeter standard in liquid helium at 0.1 MPa, is described. It is concluded that although the described test-circuit has been designed primarily for testing anemometric-type transducers, it can be used to calibrate other types of small-size LHe flowmeters also, provided they are suitable for complete immersion in liquid helium

387

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 electromagubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes

388

Preliminary Modeling of Permanent Magnet Probe Flowmeter for Voltage Signal Estimation  

International Nuclear Information System (INIS)

An experimental study on performance analysis of the flowmeter has been performed. The study shows that sodium flow rate is linearly proportional to the induced voltage signal from the flowmeter under the turbulent flow condition. The experimental results support its availability in the PDRC system. But, the flowmeter should be able to measure sodium flow at low Reynolds number as well. That is because the PDRC system uses sodium natural convection for its operation. Thus, calibration of the flowmeter should be done at very low sodium flow rates. However, Von Weissenfluh et al. showed that the relationship between flow rate and measured voltage signal from the flowmeter may become non-linear at very low flow rates. The nonlinearity restricts the utilization of level sensor which provide reference flow rate in the calibration experiment. The primary objective of this study is to predict the sodium flow rate range where the induced voltage signals are linearly proportional to flow rates by estimating the induced voltage signals against sodium flow rates for a wide range of flows numerically. A commercial code FLUENT is adopted for the analysis of flow field. And MAXWELL which is an electromagnetic analysis software using a finite volume method has been used to analyze the magnetic field generated by permanent magnet of the flowmeter. The induced voltage signals have been estimated by coupling the sodium flow field and the magnetic field using FLUENT MHD module. It is expected that the PMPF voltage signals are linearly proportional to flow rates range of 0.0059 to 1.96 lps. This suggests that simple calibration technique using the linearity between flow rate and the voltage signal can be adopted in calibration of the PMPF

389

Feasibility study of thermocouple correlation type transit time flowmeter in transient steam--water flow  

International Nuclear Information System (INIS)

Low-flow, air-water tests; low-flow, hot-water tests; and steam-water blowdown tests were performed to determine the feasibility of using a thermocouple correlation transit time flowmeter for fluid velocity measurements during Loss-of-Fluid Test blowdown experiments. The results indicate that this type of flowmeter works well in the steady flow conditions tested. However, the system does not work in transient flow experiments in which the averaging time is limited to 1 second, because thermocouple signals do not have enough high frequency content to keep the statistical noise of the correlation process down to a reasonable level

390

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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 Abstract in english 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

Marcelo José Uchoa, Corrêa; Sandro F, Perazzio; Luís Eduardo Coelho, Andrade; Cristiane, Kayser.

2010-04-01

391

Development, computer simulation and performance testing in sodium of an eddy current flowmeter  

International Nuclear Information System (INIS)

Sodium is used as a coolant in Liquid Metal Fast Breeder Reactor (LMFBR). Sodium flow measurement is of prime importance both from the operational and safety aspects of a fast reactor. Various types of flowmeters namely permanent magnet, saddle type and eddy current flowmeters are used in FBRs. From the safety point of view flow through the core should be assured under all operating conditions. This requires a flow sensor which can withstand the high temperature sodium environment and can meet the dimensional constraints and be amenable to maintenance. Eddy current flowmeter (ECFM) is one such device which meets these requirements. It is meant for measuring flow in PFBR primary pump and also at the outlets of the fuel sub-assemblies to detect flow blockage. A simulation model of ECFM was made and output of ECFM was predicted for various flowrates and temperatures. The simulation model was validated by testing in a sodium loop. This paper deals with the design, simulation and tests conducted in sodium for the eddy current flowmeter for use in the Prototype Fast Breeder Reactor (PFBR).

392

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

393

Arm locking with Doppler estimation errors  

Energy Technology Data Exchange (ETDEWEB)

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.

Yu Yinan; Wand, Vinzenz; Mitryk, Shawn; Mueller, Guido, E-mail: yinan@phys.ufl.ed [Department of Physics, University of Florida, Gainesville, FL 32611 (United States)

2010-05-01

394

Two-step Doppler cooling of a three-level ladder system with an intermediate metastable level  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Doppler laser cooling of a three-level ladder system using two near-resonant laser fields is analyzed in the case of the intermediate level being metastable while the upper level is short-lived. Analytical as well as numerical results for e.g. obtainable scattering rates and achievable temperatures are presented. When appropriate, comparisons with two-level single photon Doppler laser cooling is made. These results are relevant to recent experimental Doppler laser cooling in...

Champenois, Caroline; Hagel, Gaetan; Knoop, Martina; Houssin, Marie; Zumsteg, Cedric; Vedel, Fernande; Drewsen, Michael

2007-01-01

395

Selection and Evaluation of Magnetic Flowmeter Liner Material for Nuclear Power Plants  

International Nuclear Information System (INIS)

Nuclear power plants are licensed to operate at power levels up to a specified thermal power rating. Safety analyses and evaluations are performed at conditions selected to account for uncertainties in determining thermal power. The NRC in Regulatory Guide 1.49, Rev. 1, December 1973 provides guidance regarding the amount of margin needed to account for uncertainties. Guidance provided in Regulatory Guide 1.49 recommends that analyses and evaluations be made by assuming the thermal power is equal to 1.02 times the licensed thermal power. The reason that analyses should be performed at two percent above the licensed thermal power is to allow for possible instrument errors. A 1% error in a primary loop flow can result in a 1% reduction in the unit net load if the error is in the high direction. In order to avoid errors in the low direction (and exceeding the licensed plant thermal power) a margin is built into the control system. Improved accuracy of the primary flow measurement allows for a reduction of this margin. EPRI has reported that the typical power plant primary flow measurement errors are 3?5%. Primary loop flow measurements are used to determine the core heat rate in PWRs and as such are a basic safety indication. These measurements are conventionally made using flowmeters based on the differential pressure. Differential pressure based on flowmeters have significant, fundamental accuracy limitations as well as having failure modes difficult to diagnose whilfailure modes difficult to diagnose while in service. Magnetic flowmeters offer a potential solution to these limitations. Magnetic flowmeters are highly accurate, respond linearly, and are obstructionless (no fouling; consume no pumping power). Also, the transmitter for magnetic flowmeters can be located remotely (up to hundreds of feet) from the point of the measurement, thus reducing the environmental exposure. The major limitation to the immediate application of magnetic flowmeters to nuclear power plants is the radiation sensitivity of the non-conductive inner pipe liner. Ceramic pipe liners are currently available for pipe diameters up to 30 cm. However, for larger pipes only radiation sensitive materials such as TeflonTM or rubber are available. Ceramic pipe liners are not currently available for larger diameter pipes due to manufacturing and material limitations

396

Modelling and simulation of the dynamic performance of a natural-gas turbine flowmeter  

Energy Technology Data Exchange (ETDEWEB)

Installations involving fluids often present problems in terms of the dynamic performances of their different parts. These problems can be analysed and dealt with at the design stage. This means that both the technologists who design the thermohydraulic process and those who carry out the regulation and control must be involved in the process from the early stages of the design. In this study, a dynamic model of the behaviour of a gas flowmeter has been developed, based on the laws of conservation of mass, linear momentum, energy and angular momentum. The model has been computerised via a software module. As there is no information available with which to compare the model's behaviour, a continuous rating validation has been carried out, using a comparison with the actual calibration curve of the flowmeter. The results obtained are satisfactory. (author)

Lopez-Gonzalez, L.M. [Escuela Tecnica Superior de Ingenieria Industrial, Universidad de La Rioja, C/Luis de Ulloa, 20, E-26004 Logrono (La Rioja) (Spain); Sala, J.M.; Gonzalez-Bustamante, J.A. [Escuela Superior de Ingenieros Industriales de Bilbao, Universidad del Pais Vasco, Alameda de Urquijo, s/n 48013 Bilbao (Bizkaia) (Spain); Miguez, J.L. [Universidad de Vigo, Escuela Tecnica Superior de Ingenieros Industriales, C/Lagoas-Marcosende, s/n 36200 Vigo (Pontevedra) (Spain)

2006-11-15

397

The Doppler Pendulum Experiment  

Science.gov (United States)

An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler

Lee, C. K.; Wong, H. K.

2011-01-01

398

Doppler Optical Coherence Tomography  

Science.gov (United States)

This chapter describes Doppler optical coherence tomography (D-OCT). This is an imaging modality that combines Doppler principles with optical coherence tomography to image tissue structure and blood flow velocity simultaneously. We will review the principle and technology of D-OCT and illustrate a few examples of its applications.

Chen, Zhongping; Liu, Gangjun

399

Equations of motion of the magnetization vector in the nutation coil of a nuclear magnetic flowmeter  

Science.gov (United States)

The dependence of the nutation line shape in a nuclear magnetic flowmeter on the magnetic-field inhomogeneity in the zone of nutation-coil arrangement and the time of occurrence of the magnetized liquid under the action of a radio-frequency field in the coil has been studied by experimental and theoretical methods. The obtained experimental and theoretical data are compared, and directions of investigations to come are outlined.

Davydov, V. V.; Dudkin, V. I.; Karseev, A. Yu.

2014-10-01

400

Feasibility transient test of a correlation type transit time flowmeter in the LTSF blowdown facility  

International Nuclear Information System (INIS)

A feasibility test was made in September 1977 to determine the suitability of various transducer types as sensors for a cross-correlation type transit time flowmeter. The sensor types tested were single beam gamma densitometers, conductivity probes and passive thermocouples. Three forms of signal conditioning were applied to the thermocouple signals: bandpass amplification, frequency compensation and signal compression. The gamma densitometer was the most successful, the conductivity probe less successful and the thermocouple least successful. Further work is recommended

 
 
 
 
401