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Journal articles on the topic 'Optical pressure measurement techniques'
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1
Treaster, Delia, and W. S. Marras. "Measurement of Seat Pressure Distributions." Human Factors: The Journal of the Human Factors and Ergonomics Society 29, no. 5 (1987): 563–75. http://dx.doi.org/10.1177/001872088702900506.
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Knowledge of seating pressures is important for proper chair design. This study demonstrates the usefulness of a new methodology for measuring pressure distributions. It refines and advances an optical-reflection technique introduced several years ago. In this way precise quantitative measures of the pressure distribution can be obtained. Video image digitization, which converts analog video signals to digital ones, provided data in a form that could be easily submitted for computer analysis. Additionally, a novel method of analysis is presented that allows for the measurement and evaluation of the distribution of seated pressures, rather than peak pressures alone. A preliminary experiment with eight subjects was conducted to demonstrate the validity of the experimental apparatus and the data treatment.
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Fonov, Sergey, Grant Jones, Jim Crafton, Vladimir Fonov, and Larry Goss. "The development of optical techniques for the measurement of pressure and skin friction." Measurement Science and Technology 17, no. 6 (2006): 1261–68. http://dx.doi.org/10.1088/0957-0233/17/6/s05.
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Chacko, S. R., and S. M. Sivakumar. "A procedure for correction of creep in foam rubber optical pressure measurement techniques." Experimental Mechanics 39, no. 2 (1999): 125–31. http://dx.doi.org/10.1007/bf02331115.
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Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. "Optical measurement of isolated canine lung filtration coefficients after alloxan infusion." Journal of Applied Physiology 84, no. 4 (1998): 1381–87. http://dx.doi.org/10.1152/jappl.1998.84.4.1381.
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In this study, lung filtration coefficient ( K fc) was measured in eight isolated canine lung preparations by using three methods: standard gravimetric (Std), blood-corrected gravimetric (BC), and optical. The lungs were held in zone III conditions and were subjected to an average venous pressure increase of 8.79 ± 0.93 (mean ± SD) cmH2O. The permeability of the lungs was increased with an infusion of alloxan (75 mg/kg). The resulting K fc values (in milliliters ⋅ min−1 ⋅ cmH2O−1 ⋅ 100 g dry lung weight−1) measured by using Std and BC gravimetric techniques before vs. after alloxan infusion were statistically different: Std, 0.527 ± 0.290 vs. 1.966 ± 0.283; BC, 0.313 ± 0.290 vs. 1.384 ± 0.290. However, the optical technique did not show any statistical difference between pre- and postinjury with alloxan, 0.280 ± 0.305 vs. 0.483 ± 0.297, respectively. The alloxan injury, quantified by using multiple-indicator techniques, showed an increase in permeability and a corresponding decrease in reflection coefficient for albumin (ςf). Because the optical method measures the product of K fc and ςf, this study shows that albumin should not be used as an intravascular optical filtration marker when permeability is elevated. However, the optical technique, along with another means of measuring K fc (such as BC), can be used to calculate the ςfof a tracer (in this study, ςfof 0.894 at baseline and 0.348 after injury). Another important finding of this study was that the ratio of baseline-to-injury K fc values was not statistically different for Std and BC techniques, indicating that the percent contribution of slow blood-volume increases does not change because of injury.
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McNesby, Kevin L., Robert G. Daniel, Andrzej W. Miziolek, and Steven H. Modiano. "Optical Measurement of Toxic Gases Produced during Firefighting Using Halons." Applied Spectroscopy 51, no. 5 (1997): 678–83. http://dx.doi.org/10.1366/0003702971940819.
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Several optical techniques (FT-IR emission and absorption spectroscopy, mid- and near-infrared tunable diode laser absorption spectroscopy) have been used to measure toxic gases produced during inhibition of flames by halogenated hydrocarbons (Halons). Fire types studied include low-pressure premixed flames, counterflow diffusion atmospheric-pressure flames, open-air JP-8 (turbine fuel) fires, and confined JP-8 fires. Spectra are presented and analyzed for these fires inhibited by CF3Br (Halon 1301) and C3F7H (FM-200). For low-pressure premixed flames, spectra are presented which show production of the CF3 radical in methane/oxygen/Ar flames inhibited by CF3Br. For large-scale fire testing, it is shown that the type and amount of toxic gases produced during fire inhibition are highly dependent on fire conditions and temperatures and that some species not considered important (CF2O) are often produced in significant amounts. Finally, it is shown that HF production, during inhibition of vehicle fires using FM-200, is highly dependent on time to suppression.
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SALMAN, Mahmoud, Georgios K. GLANTZOUNIS, Wenxuan YANG, Fiona MYINT, George HAMILTON, and Alexander M. SEIFALIAN. "Measurement of critical lower limb tissue hypoxia by coupling chemical and optical techniques." Clinical Science 108, no. 2 (2005): 159–65. http://dx.doi.org/10.1042/cs20040175.
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It has been a long-term goal to develop non-invasive methods that can detect critical levels of tissue hypoxia to help in the management of chronic lower limb ischaemia. In the present study, skeletal muscle oxygenation was measured using a new Clark-type TCPO2 [transcutaneous PO2 (partial pressure of O2)]/PCO2 (partial pressure of CO2) monitoring system and optical NIRS (near-infrared spectroscopy) at graded levels of hypoxaemia using a rabbit model (n=6). The TCPO2/PCO2 probe was placed on the shaved hindlimb to record SPO2 (skin PO2) and SPCO2 (skin PCO2) continuously. A pair of NIRS probes were placed on the limb to monitor HbO2 (oxyhaemoglobin) and Hb (deoxyhaemoglobin). Graded hypoxaemia was achieved by stepwise reductions of FiO2 (fraction of inspired O2) from 30% to 6%. Animals were allowed to recover after each episode of hypoxia at an FiO2 of 30% as indicated by normalized arterial blood PO2. There was a significant (P<0.05) decrease in SPO2 with all grades of hypoxaemia and no significant changes in SPCO2. There was a significant (P<0.05) increase in muscle Hb with all grades of hypoxaemia and a significant (P<0.05) decrease in HbO2 when FiO2 was below 15%. A significant correlation was found between the SPO2 and HbO2 (r=0.92, P<0.001) and both were significantly correlated with arterial blood PO2 (P<0.001). The new TCPO2/PCO2 system, in addition to its application for the assessment of conditions such as chronic venous insufficiency where alteration in skin oxygenation occurs solely, also has potential in conditions such as peripheral vascular disease where both skin and muscle oxygenation may be affected.
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Schnabel, Christian, Maria Gaertner, and Edmund Koch. "Measurement of lung tissue dynamics in artificially ventilated rats with optical coherence tomography." Current Directions in Biomedical Engineering 3, no. 2 (2017): 79–81. http://dx.doi.org/10.1515/cdbme-2017-0017.
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AbstractDiseases of lung tissue and the airways become a major task for medical care and health care systems in modern industrial countries in the future. Suitable treatment methods and strategies for lung support and artificial ventilation are of dare need. Besides the obvious importance as life-saving intervention, the effects of usually used over-pressure ventilation onto the sensitive alveolar tissue are insufficiently understood. Therefore, it is of great interest to characterize lung tissue during artificial ventilation at the alveolar level. Those measurements can be used to link micromechanics of alveolar structures to mechanical properties of the whole lung like compliance and resistance measured at the ventilator device. This can be done only in animal experiments due to the fact that imaging techniques used in human diagnostics like CT or MRT fail to resolve alveolar tissue structures. The disadvantage of high-resolution techniques like optical coherence tomography (OCT) or intravital microscopy (IVM) is the need of a surgical access to the lung due to the limitation in penetration depth of these techniques. Furthermore, imaging dynamic processes with high-resolution imaging techniques during uninterrupted artificial ventilation is a challenging task. In this study, we present a measurement setup for combined imaging of conventional pressure-controlled ventilated rats and the visualization of volume changes of alveolar structures during one cycle of breath. A custom-made OCT system in combination with a triggered scanning algorithm was used to acquire time-resolved 3D OCT image data. Furthermore, this system was combined with a self-adapting autofocus function for intravital microscopy to track the lung surface keeping the tissue in focal plane. The combination of new dynamic measurement modes for OCT and IVM allows new insights into alveolar tissue and will promote the understanding of mechanical behavior during artificial ventilation.
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RUSOP, M., T. SOGA, T. JIMBO, M. UMENO, and M. SHARON. "STRUCTURAL AND ELECTRICAL PROPERTIES OF DIAMOND-LIKE CARBON THIN FILMS PREPARED IN INERT GAS CONDITION." Surface Review and Letters 12, no. 05n06 (2005): 691–96. http://dx.doi.org/10.1142/s0218625x05007712.
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The effects of ambient helium gas pressure on the optical, structural and electrical properties of the diamond-like carbon thin films from camphoric carbon soot target, deposited by pulsed laser deposition have been studied. Optical gap and electrical resistivity are found to increase initially at low ambient pressure of 0.008 Torr. With further increase in ambient pressure up to 2.6 Torr, optical gap and electrical resistivity are found to decrease. The films are characterized for their structural properties using different spectroscopic techniques such as, XPS, Raman, and FTIR spectroscopy, and surface morphological techniques like SEM and AFM, and their electrical properties using four-probe resistance measurement.
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Cristea, George Catalin, Sorina Ilina, George Pelin, Adriana Stefan, and Cristina Elisabeta Pelin. "Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin." Coatings 11, no. 9 (2021): 1093. http://dx.doi.org/10.3390/coatings11091093.
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In recent years, researchers have developed a new method of measuring the pressure on the surface using sensitive paints. This is an optical technique for determining surface pressure distributions by measuring changes in the intensity, emitted by certain excited molecules. The main advantage of the method over traditional techniques is the high resolution of the information. The only limitation of the resolution of a global map generated by the PSP (pressure-sensitive paint) technique is given by the capabilities of the image capture device. This paper describes the development of a technology for obtaining pressure-sensitive paint, in laboratory conditions, as an advanced measurement technique. The method has an application in many fields such as automotive, aerospace, or even medical.
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Klapcsik, Kálmán, Roxána Varga, and Csaba Hős. "Optimal Pressure Measurement Layout Design in Water Distribution Network Systems." Periodica Polytechnica Mechanical Engineering 62, no. 1 (2017): 51. http://dx.doi.org/10.3311/ppme.11409.
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This paper addresses the problem of locating the optimal pressure measurement points in a hydraulic system to help system management, calibration/validation of hydraulic models and measurement planning. Two approaches are discussed in the present work. The first method splits the hydraulic system by means of community concept borrowed from graph theory and uses merely the topology of the network. The resulting subsystems will have minimum number of external and maximum number of internal connections and leaves the choice of locating the single pressure measurement location per subsystem to a higher-level decision. The second technique is based on the sensitivity analysis of the hydraulic network and places the measurement points at the most sensitive locations, while trying to preserve the spatial diversity of the layout, i.e. preventing the accumulation of the measurement points within a small area of high sensitivity. The performance of both techniques is demonstrated on real-size hydraulic networks. The proposed sampling layouts are compared to classic D-optimality, A-optimality and V-optimality criterion.
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Harris, N. R., R. E. Parker, N. A. Pou, and R. J. Roselli. "Canine pulmonary filtration coefficient calculated from optical, radioisotope, and weight measurements." Journal of Applied Physiology 73, no. 6 (1992): 2648–61. http://dx.doi.org/10.1152/jappl.1992.73.6.2648.
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Three independent methods were used to estimate filtration coefficient (Kf) in isolated dog lungs perfused with low-hematocrit (Hct) blood. Pulmonary vascular pressure was increased by 12–23 cmH2O to induce fluid filtration. Average Kf (ml.min-1 x cmH2O–1 x 100 g dry wt-1) for six lungs was 0.26 +/- 0.05 (SE) with use of equations describing conservation of optically measured protein labeled with indocyanine green. Good agreement was found when a simplified version of the multiequation theory was applied to the data (0.24 +/- 0.05). Both optical estimates were lower than those predicted by constant slope (0.55 +/- 0.07) or extrapolation (1.20 +/- 0.15) techniques, which are based on changes in total lung weight. Subsequent studies in five dog lungs investigated whether the higher Kf from weight analyses could be caused by prolonged pulmonary vascular filling. We found that 51Cr-labeled red blood cells (RBCs), monitored over the lung, continued to accumulate for 30 min after vascular pressure elevations of 9–16 cmH2O.Kf was determined by subtracting computed vascular filling from total weight change (0.28 +/- 0.06) and by perfusate Hct changes determined from radiolabeled RBCs (0.23 +/- 0.04). These values were similar to those obtained from analysis of optical data with the complete model (0.30 +/- 0.06), the simplified version (0.26 +/- 0.05), and from optically determined perfusate Hct (0.16 +/- 0.03). However, constant slope (0.47 +/- 0.04) and extrapolation (0.57 +/- 0.07) computations of Kf were higher than estimates from the other methods. Our studies indicate that prolonged blood volume changes may accompany vascular pressure elevations and produce overestimates of Kf with standard weight measurement techniques. However, Kf computed from optical measurements is independent of pulmonary blood volume changes.
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Bastianini, Filippo, Raffaella Di Sante, Francesco Falcetelli, Diego Marini, and Gabriele Bolognini. "Optical Fiber Sensing Cables for Brillouin-Based Distributed Measurements." Sensors 19, no. 23 (2019): 5172. http://dx.doi.org/10.3390/s19235172.
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Brillouin distributed optical fiber sensing (Brillouin D-FOS) is a powerful technology for real-time in situ monitoring of various physical quantities, such as strain, temperature, and pressure. Compared to local or multi-point fiber optic sensing techniques, in Brillouin-based sensing, the optical fiber is interrogated along its complete length with a resolution down to decimeters and with a frequency encoding of the measure information that is not affected by changes in the optical attenuation. The fiber sensing cable plays a significant role since it must ensure a low optical loss and optimal transfer of the measured parameters for a long time and in harsh conditions, e.g., the presence of moisture, corrosion, and relevant mechanical or thermal stresses. In this paper, research and application regarding optical fiber cables for Brillouin distributed sensing are reviewed, connected, and extended. It is shown how appropriate cable design can give a significant contribution toward the successful exploitation of the Brillouin D-FOS technique.
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Kontis, K. "A review of some current research on pressure sensitive paint and thermographic phosphor techniques." Aeronautical Journal 111, no. 1122 (2007): 495–508. http://dx.doi.org/10.1017/s0001924000004747.
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Abstract The paper discusses the development and application activities within the Aero-Physics and Measurement Technology Laboratory at the University of Manchester on pressure sensitive paint and thermographic phosphor optical imaging systems for gas dynamic applications. It provides a brief review of the basic principles, fundamental theory, properties, chemical characteristics and bonding technologies associated with the two systems. A number of case studies are presented, which exhibit the range of applicability, limitations and potential for further development of the technologies.
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Ohsone, Y., G. Wu, J. Dryden, F. Zok, and A. Majumdar. "Optical Measurement of Thermal Contact Conductance Between Wafer-Like Thin Solid Samples." Journal of Heat Transfer 121, no. 4 (1999): 954–63. http://dx.doi.org/10.1115/1.2826086.
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This paper presents a noncontact optical technique for measuring the thermal contact conductance between wafer-like thin solid samples. The technique is based on heating one solid surface by a modulated laser beam and monitoring the corresponding temperature modulation of the other solid surface across the interface using the reflectance of a probe laser beam. The phase lag between the two laser signals is independent of the optical properties of the samples as well as the laser intensities, and can be related to the thermal contact conductance. A detailed theoretical analysis is presented to estimate the thermal contact conductance as well as the thermophysical properties of the solids from the phase lag measured as a function of the modulation frequency. Closed-form solutions in the high-frequency limit are derived in order to provide a simple estimation procedure. The effect of misalignment of the two lasers is studied and the conditions for robust measurements are suggested. As a benchmark for this technique, the thermal conductivity of a single crystal silicon sample was measured to within two percent of reported values. The thermal contact conductance was measured for Al-Si samples, each about 0.22 mm thick, in the pressure range of 0.8–10 MPa. In contrast to traditional contact conductance measurement techniques that require steady-state operation and insertion of thermocouples in thick solid samples, the noncontact dynamic optical technique requires much less time and is particularly well suited for electronic packaging materials that are typically in the thickness range of 0.1–5 mm. In addition, localized conductance measurements are now possible with a spatial resolution of about four times the thickness of the solid and can be used to detect interfacial voids and defects.
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Zhang, Yu, Jing Zu, and Hong Yan Zhang. "Electrothermal-Chemical Gun Chamber Pressure Measurement System Based on Digital Optical Fiber Transmission." Advanced Materials Research 472-475 (February 2012): 2121–24. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2121.
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There were problems of strong electromagnetic interfere (EMI) and floating of ground potential when the electrothermal-chemical gun (ETCG) was launched. EMI seriously affected the chamber pressure measurement, and affected the accurateness of data and the security of apparatus. The chamber pressure testing technology was put forward which adopted the field testing technique with digital storage and the digital optical fiber transmission technique. The on-site storage pressure gauge and multilayer electromagnetic shielding structure was designed. Test data real-time transmission and remote reappear are realized by using high speed digital optical transceiver module and optical fiber. This testing technology effectively solved the EMI problem, improved the reliability and safety of chamber pressure measurement. The test data provide a basis for research of interior ballistic properties of ETCG. This testing technology can be widely applied to the parameters measurement with strong electromagnetic interfere.
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Weigand, Peter, Wolfgang Meier, Xuru Duan, and Manfred Aigner. "Laser-Based Investigations of Thermoacoustic Instabilities in a Lean Premixed Gas Turbine Model Combustor." Journal of Engineering for Gas Turbines and Power 129, no. 3 (2006): 664–71. http://dx.doi.org/10.1115/1.2718224.
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Nonintrusive laser-based and optical measurements were performed in a gas turbine model combustor with a lean premixed swirl-stabilized CH4-air flame at atmospheric pressure. The main objective was to gain spatially and temporally resolved experimental data to enable the validation of numerical CFD results of oscillating flames. The investigated flame was operated at 25 kW and ϕ=0.70, and exhibited self-excited oscillations of more than 135 dB at ≈300Hz. The applied measurement techniques were three-dimensional (3D) laser doppler velocimetry (LDV) for velocity measurements, OH* chemiluminescence yielding information about the heat release and pointwise laser Raman scattering for the determination of joint probability density functions (PDFs) of the major species concentrations, temperature, and mixture fraction. Each of these techniques was applied with phase resolution with respect to the periodic fluctuation of the pressure in the combustion chamber that was measured with a microphone probe. The measurements finally revealed that the mixing of fuel and air in this technical premixing system was strongly affected by the pressure fluctuations leading to changes in equivalence ratio during an oscillation cycle that, in turn, induced the pressure fluctuations.
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Gold, D. M., P. M. Celliers, G. W. Collins, et al. "Interferometric and Chirped Optical Probe Techniques for High‐Pressure Equation‐of‐State Measurements." Astrophysical Journal Supplement Series 127, no. 2 (2000): 333–37. http://dx.doi.org/10.1086/313345.
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Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. "Optical measurement of isolated canine lung filtration coefficients at normal hematocrits." Journal of Applied Physiology 83, no. 6 (1997): 1976–85. http://dx.doi.org/10.1152/jappl.1997.83.6.1976.
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Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. Optical measurement of isolated canine lung filtration coefficients at normal hematocrits. J. Appl. Physiol. 83(6): 1976–1985, 1997.—In this study, lung filtration coefficient ( K fc) values were measured in eight isolated canine lung preparations at normal hematocrit values using three methods: gravimetric, blood-corrected gravimetric, and optical. The lungs were kept in zone 3 conditions and subjected to an average venous pressure increase of 10.24 ± 0.27 (SE) cmH2O. The resulting K fc(ml ⋅ min−1 ⋅ cmH2O−1 ⋅ 100 g dry lung wt−1) measured with the gravimetric technique was 0.420 ± 0.017, which was statistically different from the K fc measured by the blood-corrected gravimetric method (0.273 ± 0.018) or the product of the reflection coefficient (ςf) and K fc measured optically (0.272 ± 0.018). The optical method involved the use of a Cellco filter cartridge to separate red blood cells from plasma, which allowed measurement of the concentration of the tracer in plasma at normal hematocrits (34 ± 1.5). The permeability-surface area product was measured using radioactive multiple indicator-dilution methods before, during, and after venous pressure elevations. Results showed that the surface area of the lung did not change significantly during the measurement of K fc. These studies suggest that ςf K fccan be measured optically at normal hematocrits, that this measurement is not influenced by blood volume changes that occur during the measurement, and that the optical ςf K fcagrees with the K fc obtained via the blood-corrected gravimetric method.
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Kim, Kyeong Suk, Chan Sik Park, Dong Pyo Hong, Man Yong Choi, Ho Seob Chang, and Hyun Chul Jung. "Defect Size Measurement of Wall Thinned Pipe Using Shearography and Digital Image Correlation." Key Engineering Materials 488-489 (September 2011): 494–97. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.494.
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Defect size of wall thinned pipe is measured by using Speckle Shearing Interferometry (SSI) and Digital Image Correlation (DIC) techniques. A wall thinned defect of a carbon steel pipe was typically caused by flow accelerated corrosion (FAC). As wall thinned pipe can cause a huge accident at the nuclear power plant (NPP), a wall thinned defect should be detected for structure safety. SSI is one of the optical nondestructive techniques and can provide to inspect in real-time and to measure on the whole visible area at a time. DIC is a kind of the visual testing method. This method which uses a stereo vision system can measure the deformation or strain/stress of a structure in 3D. In this paper, ASTM A106 Gr.B carbon steel pipe is used as specimen. When the pressure load is provided by the pressure pump, the out-of-plane deformation along the longitudinal direction of a pipe can be detected quantitatively. Both results of SSI and DIC experiments are compared.
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Huang, Kuan-Hua, Fu Tan, Tzung-Dau Wang, and Yao-Joe Yang. "A Highly Sensitive Pressure-Sensing Array for Blood Pressure Estimation Assisted by Machine-Learning Techniques." Sensors 19, no. 4 (2019): 848. http://dx.doi.org/10.3390/s19040848.
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This work describes the development of a pressure-sensing array for noninvasive continuous blood pulse-wave monitoring. The sensing elements comprise a conductive polymer film and interdigital electrodes patterned on a flexible Parylene C substrate. The polymer film was patterned with microdome structures to enhance the acuteness of pressure sensing. The proposed device uses three pressure-sensing elements in a linear array, which greatly facilitates the blood pulse-wave measurement. The device exhibits high sensitivity (−0.533 kPa−1) and a fast dynamic response. Furthermore, various machine-learning algorithms, including random forest regression (RFR), gradient-boosting regression (GBR), and adaptive boosting regression (ABR), were employed for estimating systolic blood pressure (SBP) and diastolic blood pressure (DBP) from the measured pulse-wave signals. Among these algorithms, the RFR-based method gave the best performance, with the coefficients of determination for the reference and estimated blood pressures being R2 = 0.871 for SBP and R2 = 0.794 for DBP, respectively.
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Kumar, Shashi, Pradeep Kumar Rathore, Brishbhan Singh Panwar, and Jamil Akhtar. "Development of a current mirror-integrated pressure sensor using CMOS-MEMS cofabrication techniques." Microelectronics International 35, no. 4 (2018): 203–10. http://dx.doi.org/10.1108/mi-05-2017-0022.
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Purpose This paper aims to describe the fabrication and characterization of current mirror-integrated microelectromechanical systems (MEMS)-based pressure sensor. Design/methodology/approach The integrated pressure-sensing structure consists of three identical 100-µm long and 500-µm wide n-channel MOSFETs connected in a resistive loaded current mirror configuration. The input transistor of the mirror acts as a constant current source MOSFET and the output transistors are the stress sensing MOSFETs embedded near the fixed edge and at the center of a square silicon diaphragm to sense tensile and compressive stresses, respectively, developed under applied pressure. The current mirror circuit was fabricated using standard polysilicon gate complementary metal oxide semiconductor (CMOS) technology on the front side of the silicon wafer and the flexible pressure sensing square silicon diaphragm, with a length of 1,050 µm and width of 88 µm, was formed by bulk micromachining process using tetramethylammonium hydroxide solution on the backside of the wafer. The pressure is monitored by the acquisition of drain voltages of the pressure sensing MOSFETs placed near the fixed edge and at the center of the diaphragm. Findings The current mirror-integrated pressure sensor was successfully fabricated and tested using in-house developed pressure measurement system. The pressure sensitivity of the tested sensor was found to be approximately 0.3 mV/psi (or 44.6 mV/MPa) for pressure range of 0 to 100 psi. In addition, the pressure sensor was also simulated using Intellisuite MEMS Software and simulated pressure sensitivity of the sensor was found to be approximately 53.6 mV/MPa. The simulated and measured pressure sensitivities of the pressure sensor are in close agreement. Originality/value The work reported in this paper validates the use of MOSFETs connected in current mirror configuration for the measurement of tensile and compressive stresses developed in a silicon diaphragm under applied pressure. This current mirror readout circuitry integrated with MEMS pressure-sensing structure is new and fully compatible to standard CMOS processes and has a promising application in the development CMOS-MEMS-integrated smart sensors.
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Martinez, Gabrielle L., Farzad Poursadegh, Gina M. Magnotti, et al. "Measurement of Sauter mean diameter in diesel sprays using a scattering–absorption measurement ratio technique." International Journal of Engine Research 20, no. 1 (2018): 6–17. http://dx.doi.org/10.1177/1468087418819912.
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A new diagnostic for the quantification of Sauter mean diameter in high-pressure fuel sprays has been recently developed using combined optical and X-ray measurements at the Georgia Institute of Technology and Argonne National Laboratory, respectively. This diagnostic utilizes liquid scattering extinction measurements from diffuse back-illumination imaging, conducted at Georgia Tech, and liquid absorption measurements from X-ray radiography, conducted at Argonne’s Advanced Photon Source. The new diagnostic, entitled the scattering–absorption measurement ratio, quantifies two-dimensional distributions of path-integrated Sauter mean diameter, enabling the construction of the spatial history of drop size development within practical fuel sprays. This technique offers unique benefits over conventional drop-sizing methods in that it can be more robust in optically dense regions of the spray, while also providing high spatial resolution of the corresponding droplet field. The methodology for quantification of Sauter mean diameter distributions using the scattering–absorption measurement ratio technique has been previously introduced and demonstrated in diesel sprays using the Engine Combustion Network Spray D injector; however, a more detailed treatment of measurement uncertainties has been needed. In this work, we present a summary of the various sources of measurement uncertainty in the scattering–absorption measurement ratio diagnostic, like those due to the experimental setup, data processing methods, and theoretical assumptions, and assess how these sources of uncertainty affect the quantified Sauter mean diameter. The spatially resolved Sauter mean diameter measurements that result from the scattering–absorption measurement ratio diagnostic will be especially valuable to the engine modeling community for the quantitative validation of spray submodels in engine computational fluid dynamics codes. Careful evaluation and quantification of measurement uncertainties are important to support accurate model validation and to ensure the development of more predictive spray models.
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Reed, Chris, Charlotte A. Brumby, Leigh R. Crilley, et al. "HONO measurement by differential photolysis." Atmospheric Measurement Techniques 9, no. 6 (2016): 2483–95. http://dx.doi.org/10.5194/amt-9-2483-2016.
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Abstract. Nitrous acid (HONO) has been quantitatively measured in situ by differential photolysis at 385 and 395 nm, and subsequent detection as nitric oxide (NO) by the chemiluminescence reaction with ozone (O3). The technique has been evaluated by Fourier transform infrared (FT-IR) spectroscopy to provide a direct HONO measurement in a simulation chamber and compared side by side with a long absorption path optical photometer (LOPAP) in the field. The NO–O3 chemiluminescence technique is robust, well characterized, and capable of sampling at low pressure, whilst solid-state converter technology allows for unattended in situ HONO measurements in combination with fast time resolution and response.
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Awang, Rozidawati, Goh Boon Tong, Siti Meriam Ab. Gani, Richard Ritikos, and Saadah Abdul Rahman. "The Effects of Deposition Pressure on the Optical and Structural Properties of d.c. PECVD Hydrogenated Amorphous Carbon Films." Materials Science Forum 517 (June 2006): 81–84. http://dx.doi.org/10.4028/www.scientific.net/msf.517.81.
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A direct-current plasma enhanced chemical vapour deposition (PECVD) system was designed and built in-house for the deposition of hydrogenated amorphous carbon(a-C:H) thin films. In this work, a-C:H thin films prepared using this system at different deposition pressures were studied. The influence of deposition pressure on the deposition rate, energy gap, bonded hydrogen content and structure of the film has been investigated. The characterization techniques were determined from optical transmission spectroscopy, Fourier transform infrared spectroscopy and Xray diffraction measurements. The results demonstrated that the deposition pressure had strong influence on the deposition rate, optical energy gap and the bonded H content in the film. Evidence of crystallinity was observed in films prepared at low deposition pressure.
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Camacho-Lopez, Santiago, Carlos Andrés Zuñiga-Romero, Luis Felipe Devia-Cruz, Carolina Alvarez-Delgado, Marcos Antonio Plata-Sanchez, and Leopoldo Martinez-Manuel. "Intraocular Pressure Study in Ex Vivo Pig Eyes by the Laser-Induced Cavitation Technique: Toward a Non-Contact Intraocular Pressure Sensor." Applied Sciences 10, no. 7 (2020): 2281. http://dx.doi.org/10.3390/app10072281.
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Traditional applanation tonometry techniques lack the necessary accuracy and reliability for measuring the intraocular pressure (IOP), and there is still a need for a reliable technique for in vivo diagnosis. A single laser-induced cavitation bubble event was optically monitored in order to precisely measure the first collapse time of the cavitation bubble, which presents a direct dependence on the liquid pressure. This can certainly be done within the IOP range. We now extend the partial transmittance modulation (STM) technique to determine its feasibility for directly measuring the IOP by studying the nanosecond (ns) pulsed laser-induced cavitation bubble dynamics for an externally pressurized fresh ex vivo porcine eye. The results demonstrate that it is possible to monitor the IOP by detecting the light of a continuous-wave (CW) laser beam which is intensity modulated by the bubble itself. This technique currently presents a measurement resolution of about 4 mmHg in the 5 to 50 mmHg pressure range, indicating the feasibility of this approach for measuring IOP. This technique provides a direct measurement within the anterior eye chamber, avoiding common pitfalls in IOP diagnosis, such as errors due to patient movement, varying physical properties of the eye globe, or central cornea thickness (CCT) effects.
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Chen, Zengshun, Yemeng Xu, Hailin Huang, and Kam Tim Tse. "Wind Tunnel Measurement Systems for Unsteady Aerodynamic Forces on Bluff Bodies: Review and New Perspective." Sensors 20, no. 16 (2020): 4633. http://dx.doi.org/10.3390/s20164633.
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Wind tunnel tests have become one of the most effective ways to evaluate aerodynamics and aeroelasticity in bluff bodies. This paper has firstly overviewed the development of conventional wind tunnel test techniques, including high frequency base balance technique, static synchronous multi-pressure sensing system test technique and aeroelastic test, and summarized their advantages and shortcomings. Subsequently, two advanced test approaches, a forced vibration test technique and hybrid aeroelastic- force balance wind tunnel test technique have been comprehensively reviewed. Then the characteristics and calculation procedure of the conventional and advanced wind tunnel test techniques were discussed and summarized. The results indicated that the conventional wind tunnel test techniques ignored the effect of structural oscillation on the measured aerodynamics as the test model is rigid. A forced vibration test can include that effect. Unfortunately, a test model in a forced vibration test cannot respond like a structure in the real world; it only includes the effect of structural oscillation on the surrounding flow and cannot consider the feedback from the surrounding flow to the oscillation test model. A hybrid aeroelastic-pressure/force balance test technique that can observe unsteady aerodynamics of a test model during its aeroelastic oscillation completely takes the effect of structural oscillation into consideration and is, therefore, effective in evaluation of aerodynamics and aeroelasticity in bluff bodies. This paper has not only advanced our understanding for aerodynamics and aeroelasticity in bluff bodies, but also provided a new perspective for advanced wind tunnel test techniques that can be used for fundamental studies and engineering applications.
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Shen, Shaicheng, Zhiming Fang, and Xiaochun Li. "Laboratory Measurements of the Relative Permeability of Coal: A Review." Energies 13, no. 21 (2020): 5568. http://dx.doi.org/10.3390/en13215568.
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The relative permeability of coal to gas and water is an essential parameter for characterizing coalbed methane (CBM) reservoirs and predicting coal seam gas production, particularly in numerical simulations. Although a variety of studies related to the relative permeability of coals have been conducted, the results hardly meet the needs of practical engineering applications. To track the dynamic development of relative permeability measurements in the laboratory, discover the deficiencies, and discuss further work in this field, this paper investigates the relative permeability measurement preparation work and laboratory methods and summarizes the development of techniques used to determine the water saturation during experimentation. The previously determined relative permeability curves are also assembled and classified according to coal rank and the absolute permeability. It is found that the general operations in the relative permeability measurement process are still not standardized. The techniques applied to determine the water saturation of coal in experiments have been refined to some extent, but no optimal technique has been recognized yet. New techniques, such as the incorporation of high-precision differential pressure gauges, can be used to determine the water production during relative permeability measurement. In addition, the existing relative permeability data are limited, and no study has focused on supercritical carbon dioxide-water and mixed gas (methane and carbon dioxide)-water relative permeability measurements. To meet the requirements of actual projects, further research on this topic must be conducted.
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Basu, Saptarshi, Hang Xu, Michael W. Renfro, and Baki M. Cetegen. "In Situ Optical Diagnostics for Measurements of Water Vapor Partial Pressure in a PEM Fuel Cell." Journal of Fuel Cell Science and Technology 3, no. 1 (2005): 1–7. http://dx.doi.org/10.1115/1.2133799.
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A fiber optic coupled diode laser sensor has been constructed for in situ measurements of water vapor partial pressure in active proton-exchange membrane (PEM) fuel cell systems. The bipolar plate of a prototypical PEM fuel cell was modified to allow for transmission of a near infrared laser beam through the flow channels on either the fuel or oxidizer side of its membrane-electrode assembly. The laser wavelength was scanned over several water rotational and vibrational transitions and the light absorption was detected by measuring the transmitted laser power through the device. The intensity and line shape of the measured transition was used to extract path-averaged values for the water vapor partial pressure. Measurements were initially taken in a non-operating cell with known temperature and humidity input gas streams to calibrate and test the optical device. A technique for rapid determination of the water partial pressure was developed. The optical technique is applicable over a significant temperature and humidity operating range of a PEM fuel cell. The measurement technique was applied to an operating PEM fuel cell system to examine the effects of incoming gas humidity and load on the water vapor partial pressure variation in one of the flow channels.
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Kim, Eui Soo. "Failure Analysis of High Pressure Container using Fractography and Material Morphology." Key Engineering Materials 773 (July 2018): 287–91. http://dx.doi.org/10.4028/www.scientific.net/kem.773.287.
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High-pressure gas containers must be able to withstand high internal pressures because they store compressed gases. Otherwise, cracks or defects may lead to an explosion, which may in turn lead to a large-scale disaster. Therefore, accurate analysis of the causes of cracks or defects and various techniques for detecting cracks or defects are needed. In this research, we analyzed the failure mechanism of a high-pressure gas container through fractography using scanning electron microscopy and optical microscopy and through measurements of their mechanical and chemical properties.
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Pang, Li Li, Han Chuan Dong, Yun Shi, and Li De Fang. "Gas-Liquid Two-Phase Flow Detection Techniques Based on Internal and External Tube Differential Pressure Flowmeter." Applied Mechanics and Materials 568-570 (June 2014): 363–69. http://dx.doi.org/10.4028/www.scientific.net/amm.568-570.363.
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The gas-liquid two-phase flow exists widely in nature and in our daily life, to realize the phase flow does not separate online measurement has become an important subject in the study. Through CFD simulation experiment, the optimal structure of inner and outer tube differential pressure flowmeter prototype. Through the analysis of the experimental data, comparison of the classical theoretical models found high Chishlom prediction model error is minimum. Moisture the modified model, the relative error of measurement is better than in the range of experiment 5%.
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Bone, S. A., P. G. Cummins, P. B. Davies, and S. A. Johnson. "Measurement of Water Vapor Pressure and Activity Using Infrared Diode Laser Absorption Spectroscopy." Applied Spectroscopy 47, no. 6 (1993): 834–43. http://dx.doi.org/10.1366/0003702934066947.
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A mid-infrared laser technique is described for the accurate determination of water vapor concentration in the headspace above a liquid sample. The method is based on the measurement of the fractional absorption, at line center, of a single ro-vibrational line. A dual-beam optical arrangement, incorporating a reference vapor cell, is used to provide an active calibration for the measurement. It is shown how the absorption signals can be related to the water activity of a liquid sample. The technique has the advantages of being noninvasive, rapid, and signal-specific to water. It does, however, intrinsically have a nonlinear response to activity. This drawback is mainly a consequence of pressure broadening, and has limited the present measurements to sample temperatures in the range 268 to 293 K. In this regime the method gives a precision of ±1% for activities near unity. This limit is imposed by small fluctuations in certain environmental variables. Suitable modifications should enable operation at the ±0.1% level of accuracy over an extended temperature range.
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Pastor, José, Pablo Olmeda, Jaime Martín, and Felipe Lewiski. "Methodology for Optical Engine Characterization by Means of the Combination of Experimental and Modeling Techniques." Applied Sciences 8, no. 12 (2018): 2571. http://dx.doi.org/10.3390/app8122571.
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Optical engines allow for the direct visualization of the phenomena taking place in the combustion chamber and the application of optical techniques for combustion analysis, which makes them invaluable tools for the study of advanced combustion modes aimed at reducing pollutant emissions and increasing efficiency. An accurate thermodynamic analysis of the engine performance based on the in-cylinder pressure provides key information regarding the gas properties, the heat release, and the mixing conditions. If, in addition, optical access to the combustion process is provided, a deeper understanding of the phenomena can be derived, allowing the complete assessment of new injection-combustion strategies to be depicted. However, the optical engine is only useful for this purpose if the geometry, heat transfer, and thermodynamic conditions of the optical engine can mimic those of a real engine. Consequently, a reliable thermodynamic analysis of the optical engine itself is mandatory to accurately determine a number of uncertain parameters among which the effective compression ratio and heat transfer coefficient are of special importance. In the case of optical engines, the determination of such uncertainties is especially challenging due to their intrinsic features regarding the large mechanical deformations of the elongated piston caused by the pressure, and the specific thermal characteristics that affect the in-cylinder conditions. In this work, a specific methodology for optical engine characterization based on the combination of experimental measurements and in-cylinder 0D modeling is presented. On one hand, the method takes into account the experimental deformations measured with a high-speed camera in order to determine the effective compression ratio; on the other hand, the 0D thermodynamic analysis is used to calibrate the heat transfer model and to determine the rest of the uncertainties based on the minimization of the heat release rate residual in motored conditions. The method has been demonstrated to be reliable to characterize the optical engine, providing an accurate in-cylinder volume trace with a maximum deformation of 0.5 mm at 80 bar of peak pressure and good experimental vs. simulated in-cylinder pressure fitting.
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Sakai, E. H. "Measurement and Visualization of the Contact Pressure Distribution of Rubber Disks and Tires." Tire Science and Technology 23, no. 4 (1995): 238–55. http://dx.doi.org/10.2346/1.2137506.
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Abstract The contact conditions of a tire with the road surface have a close relationship to various properties of the tire and are among the most important characteristics in evaluating the performance of the tire. In this research, a new measurement device was developed that allows the contact stress distribution to be quantified and visualized. The measuring principle of this device is that the light absorption at the interface between an optical prism and an evenly ground or worn rubber surface is a function of contact pressure. The light absorption can be measured at a number of points on the surface to obtain the pressure distribution. Using this device, the contact pressure distribution of a rubber disk loaded against a plate was measured. It was found that the pressure distribution was not flat but varied greatly depending upon the height and diameter of the rubber disk. The variation can be explained by a “spring” effect, a “liquid” effect, and an “edge” effect of the rubber disk. Next, the measurement and image processing techniques were applied to a loaded tire. A very high definition image was obtained that displayed the true contact area, the shape of the area, and the pressure distribution from which irregular wear was easily detected. Finally, the deformation of the contact area and changes in the pressure distribution in the tread rubber block were measured when a lateral force was applied to the loaded tire.
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Karlen, Sylvain, Jean Gobet, Thomas Overstolz, Jacques Haesler, and Steve Lecomte. "Quantitative Micro-Raman Spectroscopy for Partial Pressure Measurement in Small Volumes." Applied Spectroscopy 71, no. 12 (2017): 2707–13. http://dx.doi.org/10.1177/0003702817724410.
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We demonstrate the quantitative capabilities of Raman confocal microscopy as a nondestructive method to measure the partial pressure of molecular gases in mm3 range sealed volume having an optical access. Thanks to a calibration procedure, we apply this technique for the characterization of the absolute nitrogen partial pressure inside buffered micro electromechanical system (MEMS) atomic vapor cells developed for atomic clocks. Our results are compared with measurements obtained by rubidium hyperfine frequency spectroscopy and a good agreement is demonstrated between the two methods, with a three-sigma detection limit below 10 mbar for a 1 h integration time, using a 33 mW 532 nm excitation laser. These results prove the potential of confocal micro-Raman spectroscopy as a simple and nondestructive method for small-scale pressure measurements.
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Kawaharada, Noritsune, Lennart Thimm, Toni Dageförde, Karsten Gröger, Hauke Hansen, and Friedrich Dinkelacker. "Approaches for Detailed Investigations on Transient Flow and Spray Characteristics during High Pressure Fuel Injection." Applied Sciences 10, no. 12 (2020): 4410. http://dx.doi.org/10.3390/app10124410.
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High pressure injection systems have essential roles in realizing highly controllable fuel injections in internal combustion engines. The primary atomization processes in the near field of the spray, and even inside the injector, determine the subsequent spray development with a considerable impact on the combustion and pollutant formation. Therefore, the processes should be understood as much as possible; for instance, to develop mathematical and numerical models. However, the experimental difficulties are extremely high, especially near the injector nozzle or inside the nozzle, due to the very small geometrical scales, the highly concentrated optical dense spray processes and the high speed and drastic transient nature of the spray. In this study, several unique and partly recently developed techniques are applied for detailed measurements on the flow inside the nozzle and the spray development very near the nozzle. As far as possible, the same three-hole injector for high pressure diesel injection is used to utilize and compare different measurement approaches. In a comprehensive section, the approach is taken to discuss the measurement results in comparison. It is possible to combine the observations within and outside the injector and to discuss the entire spray development processes for high pressure diesel sprays. This allows one to confirm theories and to provide detailed and, in parts, even quantitative data for the validation of numerical models.
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Hasell, Tom, Jayne A. Armstrong, Kim E. Jelfs, et al. "High-pressure carbon dioxide uptake for porous organic cages: comparison of spectroscopic and manometric measurement techniques." Chemical Communications 49, no. 82 (2013): 9410. http://dx.doi.org/10.1039/c3cc45924a.
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Zhang, Yong Cun, Liu Sheng Chen, Jin Kui Shang, et al. "Application of Two-Component Pressure Sensitive Paint in Transonic Wind Tunnel." Advanced Materials Research 216 (March 2011): 181–87. http://dx.doi.org/10.4028/www.scientific.net/amr.216.181.
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As a new optical pressure sensor technique, Pressure Sensitive Paint (PSP) is one of the important techn iques for model surface p ressure m easurement in wind tunnel test s . With the help of PSP , it is possible to do p ressure m easurement on compl icated or special model surface , which is usually difficult to be measured by pressure tap s . Since PSP technique being introduced into China from TsAGI (Russia) , AVIC ARI has investigated two-component PSP technique in high-speed wind tunnel in cooperati on with ICCAS China . T his report present s the principle of PSP technique, test control system development and the test result comparison s between PSP technique with two-component pressure sensitive paint FOP-2 and classic tap measurement on wing surface of an airplane model . T he results showed that the two-component pressure sensitive paint has better performance and can be used for model pressure measurement.
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Rajendran, Dhivakar, Rajarajan Ramalingame, Saravanan Palaniyappan, Guntram Wagner, and Olfa Kanoun. "Flexible Ultra-Thin Nanocomposite Based Piezoresistive Pressure Sensors for Foot Pressure Distribution Measurement." Sensors 21, no. 18 (2021): 6082. http://dx.doi.org/10.3390/s21186082.
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Foot pressure measurement plays an essential role in healthcare applications, clinical rehabilitation, sports training and pedestrian navigation. Among various foot pressure measurement techniques, in-shoe sensors are flexible and can measure the pressure distribution accurately. In this paper, we describe the design and characterization of flexible and low-cost multi-walled carbon nanotubes (MWCNT)/Polydimethylsiloxane (PDMS) based pressure sensors for foot pressure monitoring. The sensors have excellent electrical and mechanical properties an show a stable response at constant pressure loadings for over 5000 cycles. They have a high sensitivity of 4.4 kΩ/kPa and the hysteresis effect corresponds to an energy loss of less than 1.7%. The measurement deviation is of maximally 0.13% relative to the maximal relative resistance. The sensors have a measurement range of up to 330 kPa. The experimental investigations show that the sensors have repeatable responses at different pressure loading rates (5 N/s to 50 N/s). In this paper, we focus on the demonstration of the functionality of an in-sole based on MWCNT/PDMS nanocomposite pressure sensors, weighing approx. 9.46 g, by investigating the foot pressure distribution while walking and standing. The foot pressure distribution was investigated by measuring the resistance changes of the pressure sensors for a person while walking and standing. The results show that pressure distribution is higher in the forefoot and the heel while standing in a normal position. The foot pressure distribution is transferred from the heel to the entire foot and further transferred to the forefoot during the first instance of the gait cycle.
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Baker, Wesley B., Ramani Balu, Lian He, et al. "Continuous non-invasive optical monitoring of cerebral blood flow and oxidative metabolism after acute brain injury." Journal of Cerebral Blood Flow & Metabolism 39, no. 8 (2019): 1469–85. http://dx.doi.org/10.1177/0271678x19846657.
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Rapid detection of ischemic conditions at the bedside can improve treatment of acute brain injury. In this observational study of 11 critically ill brain-injured adults, we employed a monitoring approach that interleaves time-resolved near-infrared spectroscopy (TR-NIRS) measurements of cerebral oxygen saturation and oxygen extraction fraction (OEF) with diffuse correlation spectroscopy (DCS) measurement of cerebral blood flow (CBF). Using this approach, we demonstrate the clinical promise of non-invasive, continuous optical monitoring of changes in CBF and cerebral metabolic rate of oxygen (CMRO2). In addition, the optical CBF and CMRO2 measures were compared to invasive brain tissue oxygen tension (PbtO2), thermal diffusion flowmetry CBF, and cerebral microdialysis measures obtained concurrently. The optical CBF and CMRO2 information successfully distinguished between ischemic, hypermetabolic, and hyperemic conditions that arose spontaneously during patient care. Moreover, CBF monitoring during pressor-induced changes of mean arterial blood pressure enabled assessment of cerebral autoregulation. In total, the findings suggest that this hybrid non-invasive neurometabolic optical monitor (NNOM) can facilitate clinical detection of adverse physiological changes in brain injured patients that are otherwise difficult to measure with conventional bedside monitoring techniques.
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Kim, Bubryur, N. Yuvaraj, K. R. Sri Preethaa, Gang Hu, and Dong-Eun Lee. "Wind-Induced Pressure Prediction on Tall Buildings Using Generative Adversarial Imputation Network." Sensors 21, no. 7 (2021): 2515. http://dx.doi.org/10.3390/s21072515.
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Wind tunnel testing techniques are the main research tools for evaluating the wind loadings of buildings. They are significant in designing structurally safe and comfortable buildings. The wind tunnel pressure measurement technique using pressure sensors is significant for assessing the cladding pressures of buildings. However, some pressure sensors usually fail and cause loss of data, which are difficult to restore. In the literature, numerous techniques are implemented for imputing the single instance data values and data imputation for multiple instantaneous time intervals with accurate predictions needs to be addressed. Thus, the data imputation capacity of machine learning models is used to predict the missing wind pressure data for tall buildings in this study. A generative adversarial imputation network (GAIN) is proposed to predict the pressure coefficients at various instantaneous time intervals on tall buildings. The proposed model is validated by comparing the performance of GAIN with that of the K-nearest neighbor and multiple imputations by chained equation models. The experimental results show that the GAIN model provides the best fit, achieving more accurate predictions with the minimum average variance and minimum average standard deviation. The average mean-squared error for all four sides of the building was the minimum (0.016), and the average R-squared error was the maximum (0.961). The proposed model can ensure the health and prolonged existence of a structure based on wind environment.
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Cortese, Alejandro J., Conrad L. Smart, Tianyu Wang, et al. "Microscopic sensors using optical wireless integrated circuits." Proceedings of the National Academy of Sciences 117, no. 17 (2020): 9173–79. http://dx.doi.org/10.1073/pnas.1919677117.
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We present a platform for parallel production of standalone, untethered electronic sensors that are truly microscopic, i.e., smaller than the resolution of the naked eye. This platform heterogeneously integrates silicon electronics and inorganic microlight emitting diodes (LEDs) into a 100-μm-scale package that is powered by and communicates with light. The devices are fabricated, packaged, and released in parallel using photolithographic techniques, resulting in ∼10,000 individual sensors per square inch. To illustrate their use, we show proof-of-concept measurements recording voltage, temperature, pressure, and conductivity in a variety of environments.
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Fahey, D. W., R. S. Gao, O. Möhler, et al. "The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques." Atmospheric Measurement Techniques 7, no. 9 (2014): 3177–213. http://dx.doi.org/10.5194/amt-7-3177-2014.
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Abstract. The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques was conducted at the aerosol and cloud simulation chamber AIDA (Aerosol Interaction and Dynamics in the Atmosphere) at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere, where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, by extracting air into instrument flow systems, by locating instruments inside the chamber, or by sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the absolute accuracy of the instruments was not established. To evaluate the intercomparison, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.
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Fahey, D. W., R. S. Gao, O. Möhler, et al. "The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques." Atmospheric Measurement Techniques Discussions 7, no. 4 (2014): 3159–251. http://dx.doi.org/10.5194/amtd-7-3159-2014.
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Abstract. The AquaVIT-1 Intercomparison of Atmospheric Water Vapor Measurement Techniques was conducted at the aerosol and cloud simulation chamber AIDA at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, either by extracting air into instrument flow systems, locating instruments inside the chamber, or sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. These results indicate that the core instruments, in general, have intrinsic skill to determine unknown water vapor mixing ratios with an accuracy of at least ±20%. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.
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Parisiades, Paraskevas, Claude Payre, Jean-Paul Gonzales, et al. "Neutron diffraction at high pressure, low temperature under light irradiation." Acta Crystallographica Section A Foundations and Advances 70, a1 (2014): C395. http://dx.doi.org/10.1107/s2053273314096041.
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The exploration of multi-dimensional phase diagrams is a topical subject. However, the simultaneous variation of several control parameters such as temperature, pressure and light irradiation requires a suitably optimized sample environment, particularly when the aim of the experiment is to obtain structural information. We report on a new such sample environment, developed in the context of neutron diffraction measurements, in which the sample can be submitted to pressures up to 7 kbar, temperatures down to 1.7 K and light irradiation in the 660 to 852nm wavelength range, simultaneously. The Ti-Zr alloy pressure cell combines a high mechanical resistance over a wide temperature range with an acceptable neutron background level. The pressure medium is helium gas, ensuring the best possible hydrostatic conditions over a very broad temperature range. The low-temperature environment is obtained from an ILL-type `orange cryostat'. After focusing into an optical fiber, laser light is transmitted to the sample through a sapphire optical window implemented in the pressure cell. The laser flux density at the sample position is of ~30mW/cm2. The geometry of the set-up is optimized to offer a wide optical access (+/- 500vertical, +/-1650horizontal), particularly well suited for Laue neutron diffraction techniques. First results obtained on the pressure-photo-induced spin crossover of a model coordination complex will be presented.
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Sarker, M. A. R. "Optical Properties of Rutile Single Crystals Grown Under Pressure by Tilting-Mirror-Type Floating Zone Method." Journal of Scientific Research 7, no. 1-2 (2015): 1–9. http://dx.doi.org/10.3329/jsr.v7i1-2.18927.
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Rutile single crystals with high quality and high transparency were grown successfully by tilting-mirror-type floating zone (TMFZ) technique. The grown crystals were characterized by polarized optical microscopy, X-ray diffractometer, UV-visible spectrophotometer and etch pits density measurement. The effect of applied pressure during growth on the optical properties and defect density of the rutile crystals were investigated. It was found that the rutile crystals grown under the high oxygen pressure are bright and transparent due to the lower concentration of defects, but rutile crystals grown at ambient or lower oxygen pressure exhibit deep blue color due to presence of defects such as dislocations and grain boundaries. The crystals grown under high oxygen pressure contains no low-angle grain boundaries, indicating that it can be used for high efficiency optical devices.
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Dong, Chengli, Peter S. Hegeman, Andrew J. G. Carnegie, and Hani Elshahawi. "Downhole Measurement of Methane Content and GOR in Formation Fluid Samples." SPE Reservoir Evaluation & Engineering 9, no. 01 (2006): 7–14. http://dx.doi.org/10.2118/81481-pa.
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Summary Formation fluid sampling early in the life of a well ensures that vital information is available for timely input to field planning decisions. For example, in subsea wells, flow assurance is a major concern, and formation fluid samples from openhole logging help operators optimize investment in both upstream and downstream facilities. When a formation fluid sample is taken from a well drilled with oil-based mud (OBM), sample contamination by the OBM filtrate is a critical factor for the accurate measurement of the sample pressure/volume/temperature (PVT) properties. A technique of monitoring sample contamination from OBM filtrate uses optical means to monitor the buildup of both color- and methane-absorption signals during sampling. The technique provides real-time analysis of sample contamination. Methane detection is essential for condensates and lightly colored crude oils; for such fluids, the color buildup becomes difficult to detect, but the high methane content of these fluids makes possible a reliable methane-based OBM-contamination monitoring algorithm. Gas/oil ratio (GOR) is an important property of crude oil, and it is a vital input to the design of production facilities. Conventionally, GOR is measured at a PVT laboratory, and it may take many weeks before the laboratory can provide this critical information. In this paper, we describe the development of an in-situ GOR measurement technique, which uses the optical properties of methane and oil components in crude oil. With this technique, GOR can be measured downhole in real time, when the sample is taken, and without requiring phase separation. Downhole GOR has many advantages over the conventional GOR measurement techniques. It does not require tampering with the sample, which helps the operator maintain the fluid in a single phase during and after sampling. It also can aid in fingerprinting oils from different layers and provides early indications of GOR that can be compared to PVT lab results. Both the OBM contamination monitoring and the GOR algorithms work well for most crude oils. However, for heavy (dark) oils, the contamination prediction from the methane component and the GOR prediction become unreliable because of the color effect. In this paper, we describe the methodology for downhole GOR measurement, and we provide details of a decolorization technique to remove the color effect of dark oils from the methane, oil, and base channels in a downhole optical fluid analyzer tool. This technique significantly improves real-time contamination monitoring and GOR prediction results for dark oils. Introduction Real-time estimation of sample contamination by drilling-mud filtrate is critical for the collection of representative hydrocarbon-fluid samples in wells drilled with OBM. The hydrocarbon sample may become useless if the contamination is too high (typically above 10 to 15% for crude oils or 1 to 3% for gas condensates). In-situ sample OBM contamination can be predicted in real time by a downhole optical fluid analyzer tool, which is used as a module of a formation testing tool (Mullins and Schroer 2000; Smits et al. 1995; and Crombie et al. 1998). This is accomplished by using a technique of monitoring OBM contamination, which is based on measuring the change of methane content and color in the flowline as cleanup with the downhole pump proceeds and progressively larger fractions of formation fluid replace the OBM filtrate. An accurate value of the GOR is important for many applications, including crude-oil typing and production facilities design. Conventionally, GOR is measured in a PVT laboratory by flashing the crude oil and then measuring the volumes of the gaseous and liquid phases at standard conditions (1 atm and 60°F). It may take many weeks before the laboratory can provide this critical information. The downhole optical fluid analyzer tool has a methane channel and an oil channel, which cover the methane absorption peak and oil absorption peak, respectively. We have developed an in-situ GOR measurement technique that derives GOR from the optical density (OD) ratio of the methane channel and the oil channel. Thus, GOR can be measured downhole in real time, when the sample is taken, and while keeping the sample intact. Downhole GOR is valuable in providing an early confirmation check for subsequent laboratory PVT analysis. The downhole GOR measurement also aids fingerprinting oils from different layers and helps the operator maintain the fluid in a single phase during sampling. Both the OBM contamination monitoring and the downhole GOR techniques work well for the majority of light- to medium-colored crude oils. However, when these two techniques are applied to heavy oils, the color absorption of the crude extends to the near-infrared region (NIR) and covers the methane and oil molecular-vibration peaks. If not corrected for, this would result in errors in the methane-based contamination prediction and GOR prediction. This paper describes a decolorization algorithm to remove the color effect from the methane and the oil channels. This algorithm is based on the exponential decay of color absorption toward the longer wavelengths in the NIR region. After decolorization, the methane and oil channels contain only the molecular-vibration absorptions of methane and oil, which are then used to derive an accurate crude-oil contamination value and GOR. The examples described here involved OBM. It should be noted that all the techniques for GOR calculation mentioned in this paper can be, and have been, applied successfully to sampling in wells drilled with water-based mud.
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Kweh, C. C., H. P. Evans, and R. W. Snidle. "Elastohydrodynamic Lubrication of Heavily Loaded Circular Contacts." Proceedings of the Institution of Mechanical Engineers, Part C: Mechanical Engineering Science 203, no. 2 (1989): 133–48. http://dx.doi.org/10.1243/pime_proc_1989_203_096_02.
Full textAbstract:
The paper is concerned with theoretical analysis and experimental measurement of lubricant film thickness in heavily loaded elastohydrodynamic contacts in which the area of elastic deformation is approximately circular. The inverse elastohydrodynamic technique for numerical analysis of contacts of this type described by Evans and Snidle(9) has been used to produce solutions covering a wide range of conditions representative of engineering practice. Detailed solutions for film thickness and pressure have been obtained for conditions giving rise to maximum contact pressures of up to 4.1 GPa with steel surfaces and a mineral oil lubricant. On the basis of these results charts for film thickness have been constructed using the non-dimensional groups proposed by Moes and Bosma(12). Experimental measurements of film thickness have been made using the optical interferometry technique. The conditions used in the experiments have been numerically analysed to provide a direct comparison between theory and experiment. The comparison shows excellent agreement between the theoretical predictions and corresponding experimental measurements.
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Napoli, Anthony M. "Physiologic and Clinical Principles behind Noninvasive Resuscitation Techniques and Cardiac Output Monitoring." Cardiology Research and Practice 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/531908.
Full textAbstract:
Clinical assessment and vital signs are poor predictors of the overall hemodynamic state. Optimal measurement of the response to fluid resuscitation and hemodynamics has previously required invasive measurement with radial and pulmonary artery catheterization. Newer noninvasive resuscitation technology offers the hope of more accurately and safely monitoring a broader range of critically ill patients while using fewer resources. Fluid responsiveness, the cardiac response to volume loading, represents a dynamic method of improving upon the assessment of preload when compared to static measures like central venous pressure. Multiple new hemodynamic monitors now exist that can noninvasively report cardiac output and oxygen delivery in a continuous manner. Proper assessment of the potential future role of these techniques in resuscitation requires understanding the underlying physiologic and clinical principles, reviewing the most recent literature examining their clinical validity, and evaluating their respective advantages and limitations.
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ELAHI, SEYED ALI, NATHANAEL CONNESSON, and YOHAN PAYAN. "DISPOSABLE SYSTEM FOR IN-VIVO MECHANICAL CHARACTERIZATION OF SOFT TISSUES BASED ON VOLUME MEASUREMENT." Journal of Mechanics in Medicine and Biology 18, no. 04 (2018): 1850037. http://dx.doi.org/10.1142/s0219519418500379.
Full textAbstract:
In-vivo characterization of soft tissues is a key step toward biomechanical simulation and planning of intra-operative assisted surgery. To achieve this, aspiration method is a standard technique: tissue is aspirated through a hole while measuring the pressure and associated apex height. An inverse problem is then solved to identify the material mechanical properties. In the literature, the apex height is usually measured using a camera, which induces design difficulties, in particular in regards on the required sterilization process for in-vivo measurements. In this paper, the idea is to replace the apex height optical measurement by the measurement of the aspirated tissue volume. The proposed method enables to reduce the system head to a simple tube: sterilizations becomes easy and the system is disposable after use. The proposed system is thus the simplest, lightest and cheapest one could achieve. It is also to the authors knowledge the first time ever in aspiration method that the aspired volume is the extracted data. As the data signal-to-noise ratio is the main factor impacting any applied inverse method when extracting the mechanical properties, the aim of this work is to assess and compare the experimental signal-to-noise ratio in the raw volume measurements obtained either optically or with the method proposed. Explicit results of inverse methods using volumes as input data are not presented in this paper for concision purpose. The effects on accuracy of various experimental parameters has been investigated and quantified: the volume measurement has proved to present a same order or even better signal-to-noise ratio compared to optical measurements.
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Chowdhury, Moajjem Hossain, Md Nazmul Islam Shuzan, Muhammad E. H. Chowdhury, et al. "Estimating Blood Pressure from the Photoplethysmogram Signal and Demographic Features Using Machine Learning Techniques." Sensors 20, no. 11 (2020): 3127. http://dx.doi.org/10.3390/s20113127.
Full textAbstract:
Hypertension is a potentially unsafe health ailment, which can be indicated directly from the blood pressure (BP). Hypertension always leads to other health complications. Continuous monitoring of BP is very important; however, cuff-based BP measurements are discrete and uncomfortable to the user. To address this need, a cuff-less, continuous, and noninvasive BP measurement system is proposed using the photoplethysmograph (PPG) signal and demographic features using machine learning (ML) algorithms. PPG signals were acquired from 219 subjects, which undergo preprocessing and feature extraction steps. Time, frequency, and time-frequency domain features were extracted from the PPG and their derivative signals. Feature selection techniques were used to reduce the computational complexity and to decrease the chance of over-fitting the ML algorithms. The features were then used to train and evaluate ML algorithms. The best regression models were selected for systolic BP (SBP) and diastolic BP (DBP) estimation individually. Gaussian process regression (GPR) along with the ReliefF feature selection algorithm outperforms other algorithms in estimating SBP and DBP with a root mean square error (RMSE) of 6.74 and 3.59, respectively. This ML model can be implemented in hardware systems to continuously monitor BP and avoid any critical health conditions due to sudden changes.