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Sensors (Basel, Switzerland) Oct 2022Ultrasonic flowmeters play an important role in industrial production, aerospace and other fields. In this paper, a high-precision ultrasonic flowmeter based on the...
Ultrasonic flowmeters play an important role in industrial production, aerospace and other fields. In this paper, a high-precision ultrasonic flowmeter based on the cross-correlation method is designed, and the commercial finite element software COMSOL Multiphysics 5.6 is used to simulate the propagation process of ultrasonic waves during flow measurement, and the implementation process of the cross-correlation algorithm is simulated by Python language. The flowmeter adopts the cross-correlation algorithm to improve the measurement accuracy of ultrasonic time of flight and adopts the method of combining FPGA and an embedded microprocessor to improve operation efficiency. In order to verify the performance of the flowmeter, we tested the flowmeter on the National Institute of Metrology and the self-built test platform, using the still water dragging method, the dynamic volume method and the field comparison method, respectively. The results show that the flowmeter has the ability to test the flow under the condition of high flow velocity (26 m/s) and a pipe diameter in the range of DN6~DN1600, that the absolute value of the relative indication error does not exceed 0.815% and that the repeatability does not exceed 0.150%. The designed ultrasonic flowmeter has high measurement accuracy, good repeatability, strong stability and a wide application range.
Topics: Algorithms; Flowmeters; Rheology; Ultrasonics; Water
PubMed: 36236569
DOI: 10.3390/s22197470 -
Scientific Reports Jan 2020The effects of gradual vascular occlusion on the blood supply of perfused areas are poorly described. Information relating to the comparison of flap monitoring... (Comparative Study)
Comparative Study
The effects of gradual vascular occlusion on the blood supply of perfused areas are poorly described. Information relating to the comparison of flap monitoring techniques is lacking. Varying stenotic conditions (0%, 25%, 50%, 75% and 100%) were generated on purpose at the A. and V. femoralis in the rat model. Analyses included flowmeter, simultaneous laser-Doppler flowmetry and tissue spectrophotometry (O2C) and indocyanine green- (ICG-) videoangiography with integrated FLOW 800 tool. A Random Forests prediction model was used to analyse the importance of each method to diagnose the stenotic conditions. The ability to discriminate and to accurately estimate the probability of stenosis was assessed by Receiver Operating Characteristic (ROC) curves and calibration plots. Blood flow changes for all modalities were described in detail. Flowmeter displayed earliest a linear decrease as a result of increasing stenosis. A stenosis of 50% degrees was most difficult to detect correctly. The combination of flowmeter and ICG-videoangiography showed high diagnostic power for each stenotic situation (area under the ROC > 0.79). Flowmeter and ICG-videoangiography showed to be most relevant in detection of varying stenotic conditions and may change the clinical outcome. The O2C showed less effect on varying stenotic situations as the only surface monitoring device.
Topics: Angiography; Animals; Constriction, Pathologic; Flowmeters; Fluorescein Angiography; Free Tissue Flaps; Indocyanine Green; Laser-Doppler Flowmetry; Rats; Spectrophotometry; Videodisc Recording
PubMed: 31969630
DOI: 10.1038/s41598-020-57777-2 -
Sensors (Basel, Switzerland) Apr 2022This paper presents a microfluidic thermal flowmeter for monitoring injection pumps, which is essential to ensure proper patient treatment and reduce medication errors...
This paper presents a microfluidic thermal flowmeter for monitoring injection pumps, which is essential to ensure proper patient treatment and reduce medication errors that can lead to severe injury or death. The standard gravimetric method for flow-rate monitoring requires a great deal of preparation and laboratory equipment and is impractical in clinics. Therefore, an alternative to the standard method suitable for remote, small-scale, and frequent infusion-pump monitoring is in great demand. Here, we propose a miniaturized thermal flowmeter consisting of a silicon substrate, a platinum heater layer on a silicon dioxide thin-membrane, and a polymer microchannel to provide accurate flow-rate measurement. The present thermal flowmeter is fabricated by the micromachining and micromolding process and exhibits sensitivity, linearity, and uncertainty of 0.722 mW/(g/h), 98.7%, and (2.36 ± 0.80)%, respectively, in the flow-rate range of 0.5-2.5 g/h when the flowmeter is operated in the constant temperature mode with the channel width of 0.5 mm. The measurement range of flow rate can be easily adjusted by changing the cross-sectional microchannel dimension. The present miniaturized thermal flowmeter shows a high potential for infusion-pump calibration in clinical settings.
Topics: Calibration; Cross-Sectional Studies; Flowmeters; Humans; Microfluidics; Temperature
PubMed: 35590842
DOI: 10.3390/s22093151 -
Sensors (Basel, Switzerland) Aug 2021An innovative rapid prototyping technique for embedding microcomponents in PDMS replicas was developed and applied on a thermal mass flowmeter for closed loop micropump...
An innovative rapid prototyping technique for embedding microcomponents in PDMS replicas was developed and applied on a thermal mass flowmeter for closed loop micropump flowrate control. Crucial flowmeter design and thermal parameters were investigated with a 3-D fully coupled electro-thermal-fluidic model which was built in Comsol Multiphysics 5.2. The flowmeter was characterized for three distinct measuring configurations. For precise low flowrate applications, a sensor-heater-sensor flowmeter configuration with a constant heater temperature was found to be the most appropriate yielding the measuring range of 0 to 90 µL·min and the sensitivity of 1.3 °C·µL·min in the lower flowrate range of 0 to 40 µL·min.
Topics: Flowmeters; Temperature
PubMed: 34450811
DOI: 10.3390/s21165373 -
Sensors (Basel, Switzerland) Dec 2022Most of the studies on mechanical oscillator flowmeters were conducted in the '80s and '90s when computational fluid dynamics (CFD) was not a viable scientific tool in...
Most of the studies on mechanical oscillator flowmeters were conducted in the '80s and '90s when computational fluid dynamics (CFD) was not a viable scientific tool in flow metrology. Still, many topics related to the application of mechanical oscillator flowmeters require further investigation. In the article, a numerical model of a mechanical oscillator flowmeter is developed with the commercial software ANSYS Fluent. The model is validated against experimental data obtained at a water calibration stand. The influence of the selected turbulence model, dynamic mesh method, as well as grid and time step size is studied. The model's qualitative behavior is correct, allowing investigation into the flowmeter operation in detail. It can provide a base for the improvement of the flowmeter's performance. Relative differences in the frequency of oscillations did not exceed 4% for a DN50 flowmeter in the flow rate range (2-40) m/h.
Topics: Flowmeters; Hydrodynamics; Software
PubMed: 36616714
DOI: 10.3390/s23010116 -
The British Journal of Ophthalmology Aug 1998To study the vasoactivity of glaucoma patients with four previously described and distinct disc appearances potentially representative of primary open angle glaucoma...
AIMS/BACKGROUND
To study the vasoactivity of glaucoma patients with four previously described and distinct disc appearances potentially representative of primary open angle glaucoma subgroups.
METHODS
Patients with pure examples of four glaucomatous optic disc types--focal ischaemic, myopic glaucomatous, senile sclerotic, and those with generalised cup enlargement, were selected. A detailed ophthalmic, systemic, drug, and smoking history was taken from the patients who, in addition, underwent assessment of peripheral vasospasm with a laser Doppler flowmeter. Differences between the groups were evaluated using an analysis of variance, Student's t test, Pearson's chi 2 test, Fisher's exact test together with Spearman's and Pearson's correlation tests.
RESULTS
38 patients with focal ischaemic, 37 with myopic glaucomatous, 24 with senile sclerotic, and 24 with discs characterised by generalised cup enlargement met the selection criteria. The group of patients with focal ischaemic discs contained more women (66% versus 32%-50% in the other three groups; p = 0.01) and had a higher prevalence of vasospasm (63% versus 25%-49%; p = 0.01), migraine (32% versus 8%-19%; p = 0.02), and cold extremities (66% versus 17%-30%; p = 0.00003). The group of patients with senile sclerotic discs had a higher prevalence of systemic cardiovascular disease (58% versus 21%-30% in the other three groups; p = 0.01) and thyroid disease (21% cf 0%-8%; p = 0.01) and although their mean age was greater (76 years cf 55-65 years; p < 0.00001) the findings were independent of age. Smoking was unrelated to optic disc type.
CONCLUSION
Vasospasm, previously associated with normal tension glaucoma, and generalised cardiovascular disease both appear to be specific risk factors for the development of particular subgroups of glaucoma and may be independent of absolute intraocular pressure levels exerting effects in patients with both "normal" or "raised" intraocular pressure. The simple assessment as to whether a glaucoma patient suffers from colder extremities than average appeared to be better at distinguishing the focal ischaemic type of glaucoma than the more complex determination of vasospasm using the laser Doppler flowmeter.
Topics: Adult; Age Factors; Aged; Constriction, Pathologic; Female; Glaucoma, Open-Angle; Humans; Male; Middle Aged; Myopia; Optic Disk; Optic Nerve Diseases; Optic Neuropathy, Ischemic; Raynaud Disease; Sclerosis; Smoking; Vascular Diseases
PubMed: 9828767
DOI: 10.1136/bjo.82.8.862 -
Plastic and Reconstructive Surgery.... Sep 2017Remote monitoring capability does not currently exist for Periflux (Perimed AB, Järfälla, Sweden) laser Doppler and other perfusion monitors. Two simple adaptations...
Remote monitoring capability does not currently exist for Periflux (Perimed AB, Järfälla, Sweden) laser Doppler and other perfusion monitors. Two simple adaptations using free apps (applications) and smart devices can enable transmission of the perfusion readout to the surgeon's smartphone. A literature review was conducted to identify reports relating to remote free flap monitoring. In addition, 2 wireless methodologies are devised: One method uses a free app that converts a smart device into a camera, stationed next to the perfusion monitor, to stream live video of the laser Doppler readout to the surgeon's smartphone; a second method uses a free app installed on a bedside laptop computer, which is connected to the laser Doppler flowmeter via a data cord. A live feed of the computer's desktop as a teleconference host is transmitted to the surgeon's smart device over the Internet. These 2 methodologies were employed on 9 and 8 free flaps, respectively, as a pilot study. All free flaps were monitored remotely for 4-6 days with near 100% reliability. The Internet connectivity became disrupted only on several occasions, requiring simple Wi-Fi and software reset. Minor mechanical issues were encountered with the video streaming method. Literature review identified very few articles describing remote monitoring of free flaps. The 2 methodologies reported here provided reliable continuous transmission of quantitative data of flap perfusion to smart devices via Internet connection, which can revolutionize the microsurgeon's practice if his/her adjunctive perfusion monitor with display does not yet have Wi-Fi capability.
PubMed: 29062671
DOI: 10.1097/GOX.0000000000001507 -
Scientific Reports May 2017Haemorheology has been long identified as an early biomarker of a wide range of diseases, especially cardiovascular diseases. This study investigates for the first time...
Haemorheology has been long identified as an early biomarker of a wide range of diseases, especially cardiovascular diseases. This study investigates for the first time the suitability of Photoplethysmography (PPG) as a non-invasive diagnostic method for haemorheological changes. The sensitivity of both PPG components (AC and DC) to changes in haemorheology were rigorously investigated in an in vitro experimental setup that mimics the human circulation. A custom-made reflectance PPG sensor, a pressure transducer and an ultrasonic Doppler flowmeter were used to map changes in flow dynamics and optical responses in an arterial model. The study investigated the effect of shear rates by varying fluid pumping frequencies using 4 set-points and the effect of clot formation using a chemical trigger. Both PPG amplitudes and PPG levels showed significant (p < 0.001) changes during the increase in shear rates and an immediate change after thromboplastin activation. The findings highlight that PPG has the potential to be used as a simple non-invasive method for the detection of blood characteristics, including disaggregation, radial migration and cross-linking fibrin formations. Such capability will enable the assessment of the effects of clotting-activators and anticoagulants (including non-pharmacological methods) and might aid in the early non-invasive assessment of cardiovascular pathologies.
Topics: Animals; Blood Coagulation; Cardiovascular Diseases; Erythrocytes; Hemorheology; Horses; Photoplethysmography
PubMed: 28469198
DOI: 10.1038/s41598-017-01636-0 -
International Journal of Chronic... 2021The use of simple and affordable screening tools for chronic obstructive pulmonary disease (COPD) is limited. We aimed to assess the validity of a handheld expiratory...
PURPOSE
The use of simple and affordable screening tools for chronic obstructive pulmonary disease (COPD) is limited. We aimed to assess the validity of a handheld expiratory flowmeter (Vitalograph Ltd., COPD-6, Ireland) for COPD screening in Chinese primary care settings.
METHODS
In our cross-sectional study, subjects were randomly selected in eight primary care settings. Tests with the handheld expiratory flowmeter and the conventional spirometry were sequentially performed on all participants. The correlation between the handheld expiratory flowmeter and the conventional spirometry was determined. Validity was determined by the area under the receiver operator characteristic curve (AUC) of the forced expiratory volume in one second (FEV)forced expiratory volume in six seconds (FEV) that used to detect airway obstruction. The sensitivity, specificity, predictive values, and likelihood ratio were calculated according to different FEV/FEV cut-off points.
RESULTS
A total of 229 subjects (15.4%) were diagnosed with airflow limitation by conventional spirometry. FEV, FEV, and FEV/FEV measured by the handheld expiratory flowmeter were correlated with FEV, FVC, and FEV/FVC measured by the conventional spirometry (=0.889, 0.835 and 0.647, p<0.001), respectively. AUC of the FEV/FEV to determine airflow obstruction was 0.857 (95% CI: 0.826 to 0.888). No significant difference of AUC was observed between the symptomatic group and the asymptomatic group (AUC=0.869 vs 0.843, P=0.425). A similar phenomenon was found in the AUC of smokers and never-smokers (AUC=0.862 vs 0.840; P=0.515). The cut-off point for FEV/FEV was 0.77 and the corresponding sensitivity and specificity were 71.2% and 89.8%, respectively.
CONCLUSION
The handheld expiratory flowmeter might be used as a screening device for COPD in Chinese primary care settings.
Topics: China; Cross-Sectional Studies; Flowmeters; Forced Expiratory Volume; Humans; Primary Health Care; Pulmonary Disease, Chronic Obstructive; Spirometry; Vital Capacity
PubMed: 34267511
DOI: 10.2147/COPD.S312190 -
Frontiers in Bioengineering and... 2022Vasomotion is the spontaneous time-dependent contraction and relaxation of micro arteries and the oscillating frequency is about 0.01-0.1 Hz. The physiological...
Vasomotion is the spontaneous time-dependent contraction and relaxation of micro arteries and the oscillating frequency is about 0.01-0.1 Hz. The physiological mechanism of vasomotion has not been thoroughly understood. From the dynamics point of view, the heartbeat is the only external loading exerted on the vascular system. We speculate that the nonlinear vascular system and the variable period of the heartbeat might induce the low-frequency vasomotion. In this study, the laser Doppler flowmeter is used to measure the time series of radial artery blood flow and reconstructed modified time series that has the same period as the measured time series but different heartbeat curves. We measured the time series of radial artery blood flow in different conditions by adding different noise disturbances on the forearm, and we decomposed the experiment pulse signal by Hilbert-Huang transform. The wavelet spectral analyses showed that the low-frequency components were induced by the variable period but independent of the shape of the heartbeat curve. Furthermore, we simulated the linear flow in a single pipe and the nonlinear flow in a piping network and found that the nonlinear flow would generate low-frequency components. From the results, we could deduce that the variable period of heartbeat and the nonlinearity of the vascular system induce vasomotion. The noise has effects on the blood signals related to the respiratory activities (∼0.3 Hz) but little influence on that related to the cardiac activities (∼1 Hz). Adding white noise and then stopping would induce an SNR increase in the frequency band related to vasomotion (∼0.1 Hz).
PubMed: 35309989
DOI: 10.3389/fbioe.2022.819716