Showing papers on "Pressure measurement published in 2010"

In-Shoe Plantar Pressure Measurement and Analysis System Based on Fabric Pressure Sensing Array

Abstract: Spatial and temporal plantar pressure distributions are important and useful measures in footwear evaluation, athletic training, clinical gait analysis, and pathology foot diagnosis. However, present plantar pressure measurement and analysis systems are more or less uncomfortable to wear and expensive. This paper presents an in-shoe plantar pressure measurement and analysis system based on a textile fabric sensor array, which is soft, light, and has a high-pressure sensitivity and a long service life. The sensors are connected with a soft polymeric board through conductive yarns and integrated into an insole. A stable data acquisition system interfaces with the insole, wirelessly transmits the acquired data to remote receiver through Bluetooth path. Three configuration modes are incorporated to gain connection with desktop, laptop, or smart phone, which can be configured to comfortably work in research laboratories, clinics, sport ground, and other outdoor environments. A real-time display and analysis software is presented to calculate parameters such as mean pressure, peak pressure, center of pressure (COP), and shift speed of COP. Experimental results show that this system has stable performance in both static and dynamic measurements.

Arterial blood pressure measurement and pulse wave analysis?their role in enhancing cardiovascular assessment

Abstract: The most common method of clinical measurement of arterial blood pressure is by means of the cuff sphygmomanometer. This instrument has provided fundamental quantitative information on arterial pressure in individual subjects and in populations and facilitated estimation of cardiovascular risk related to levels of blood pressure obtained from the brachial cuff. Although the measurement is taken in a peripheral limb, the values are generally assumed to reflect the pressure throughout the arterial tree in large conduit arteries. Since the arterial pressure pulse becomes modified as it travels away from the heart towards the periphery, this is generally true for mean and diastolic pressure, but not for systolic pressure, and so pulse pressure. The relationship between central and peripheral pulse pressure depends on propagation characteristics of arteries. Hence, while the sphygmomanometer gives values of two single points on the pressure wave (systolic and diastolic pressure), there is additional information that can be obtained from the time-varying pulse waveform that enables an improved quantification of the systolic load on the heart and other central organs. This topical review will assess techniques of pressure measurement that relate to the use of the cuff sphygmomanometer and to the non-invasive registration and analysis of the peripheral and central arterial pressure waveform. Improved assessment of cardiovascular function in relation to treatment and management of high blood pressure will result from future developments in the indirect measurement of arterial blood pressure that involve the conventional cuff sphygmomanometer with the addition of information derived from the peripheral arterial pulse.

Design and Modeling of a Textile Pressure Sensor for Sitting Posture Classification

Abstract: A textile pressure sensor has been designed for measuring pressure distribution on the human body. Electrodes built with conductive textiles are arranged on both sides of a compressible spacer, forming a variable capacitor. The use of textiles makes unobtrusive, comfortable, lightweight, and washable sensors possible. This simplifies the goal to integrate such sensors into clothing in the future, to be simple, and fast to mount just as getting dressed. Hysteresis induced by the spacer of the sensor has been modeled with the Preisach model to reduce the measurement error from 24% to 5% on average and the maximal error from above 50% to below 10%. Standard textiles that are not specially optimized for low hysteresis can be used for designing the sensor due to the modeling. The model may also be used for other pressure or even strain sensors to reduce their hysteresis. The modeling enhances the accuracy of the textile sensor to those of commercial, nontextile pressure sensing mats. Furthermore, we used the sensor system for the classification of sitting postures in a chair. The data of nine subjects have been classified with Naive Bayes classifier, achieving an average recognition rate of 82%. We show that the textile sensor performs similarly to a commercial, nontextile pressure sensing mat for this application.

Highly birefringent microstructured fibers with enhanced sensitivity to hydrostatic pressure.

Abstract: We designed, manufactured and characterized two birefringent microstructured fibers that feature a 5-fold increase in polarimetric sensitivity to hydrostatic pressure compared to the earlier reported values for microstructured fibers. We demonstrate a good agreement between the finite element simulations and the experimental values for the polarimetric sensitivity to pressure and to temperature. The sensitivity to hydrostatic pressure has a negative sign and exceeds −43 rad/MPa × m at 1.55 μm for both fibers. In combination with the very low sensitivity to temperature, this makes our fibers the candidates of choice for the development of microstructured fiber based hydrostatic pressure measurement systems.

High pressure sensor based on photonic crystal fiber for downhole application

Abstract: We demonstrate a polarization-maintaining (PM) photonic crystal fiber (PCF) based Sagnac interferometer for downhole high pressure sensing application. The PM PCF serves as a direct pressure sensing probe. The sensor is transducer free and thus fundamentally enhances its long-term sensing stability. In addition, the PM PCF can be coiled into a small diameter to fulfill the compact size requirement of downhole application. A theoretical study of its loss and birefringence changes with different coiling diameters has been carried out. This bend-insensitive property of the fiber provides ease for sensor design and benefits practical application. The pressure sensitivities of the proposed sensor are 4.21 and 3.24 nm/MPa at ∼1320 and ∼1550 nm, respectively. High pressure measurement up to 20 MPa was achieved with our experiment. It shows both good linearity in response to applied pressure and good repeatability within the entire measurement range. The proposed pressure sensor exhibits low temperature cross sensitivity and high temperature sustainability. It functions well without any measurable degradation effects on sensitivity or linearity at a temperature as high as 293 °C. These characteristics make it a potentially ideal candidate for downhole pressure sensing.

Multi-time-delay LSE-POD complementary approach applied to unsteady high-Reynolds-number near wake flow

Abstract: This investigation compared the application and accuracy of single- and multi-time-delay linear stochastic estimation-proper orthogonal decomposition (LSE-POD) methods in the temporal domain. These methods were considered for low-dimensional estimations of the dynamics of the energy-containing structures in a high Reynolds number flow. The near wake dynamics of a bluff body were used to demonstrate the robustness and accuracy of the investigated LSE-POD methods. Statistically independent two-dimensional particle image velocimetry (PIV) measurements were used to determine spatial POD modes, and time-resolved surface pressure measurements were used to determine LSE coefficients required for estimating the time-varying POD coefficients. A low-order, time-resolved reconstruction of the wake dynamics was accomplished using these estimated time-varying POD coefficients. The paper also provides details concerning the accuracy of the estimation using multi-time-delay LSE-POD. The results demonstrate that the multi-time LSE-POD technique is successful in capturing and reconstructing the important near wake dynamics. It is also shown that optimizing the time delays used for the estimations increases the accuracy of the reconstruction. As a result of its capabilities, the multi-time-delay implementation of the LSE-POD approach offers an alternate method for low-dimensional modeling that is attractive for real-time flow estimation.

Media-compatible electrically isolated pressure sensor for high temperature applications

Abstract: A pressure sensor is described with sensing elements electrically and physically isolated from a pressurized medium. An absolute pressure sensor has a reference cavity, which can be at a vacuum or zero pressure, enclosing the sensing elements. The reference cavity is formed by bonding a recessed cap wafer with a gauge wafer having a micromachined diaphragm. Sensing elements are disposed on a first side of the diaphragm. The pressurized medium accesses a second side of the diaphragm opposite to the first side where the sensing elements are disposed. A spacer wafer may be used for structural support and stress relief of the gauge wafer. In one embodiment, vertical through-wafer conductive vias are used to bring out electrical connections from the sensing elements to outside the reference cavity. In an alternative embodiment, peripheral bond pads on the gauge wafer are used to bring out electrical connections from the sensing elements to outside the reference cavity

Eccentric pressure catheter with guidewire compatibility

Abstract: There is herein described a catheter for measuring a pressure in a cardiovascular system. The catheter comprises: a guiding tube adapted for insertion into the cardiovascular system. The guiding tube defines a lumen for sliding a guidewire therethrough. The catheter further comprises a tip pressure sensor eccentrically mounted relative to the guiding tube and a signal communication means extending therefrom. The tip pressure sensor is for sensing a pressure in the cardiovascular system and the signal communicating means is for transmitting a signal indicative of the pressure to a processing device in order to obtain a pressure measurement reading.

Saturated Pressure Measurements of 2,3,3,3-Tetrafluoroprop-1-ene (HFO-1234yf)

Abstract: The vapor pressure data of 2,3,3,3-tetrafluoroprop-1-ene (CF3CF═CH2, HFO-1234yf) were measured using a constant-volume apparatus. Measurements were carried out in a wide temperature range, from (224 to 366) K, and at pressures from (39 to 3218) kPa. A total of 35 experimental points were obtained. The measurements were fitted to the Wagner equation with an absolute deviation of 0.35 %. To our knowledge, no other experimental results have been published in the open literature on the properties studied here; for this reason, our experimental results were compared with a preliminary equation of state.

Automated high pressure cell for pressure jump x-ray diffraction

Abstract: A high pressure cell for small and wide-angle x-ray diffraction measurements of soft condensed matter samples has been developed, incorporating a fully automated pressure generating network. The system allows both static and pressure jump measurements in the range of 0.1-500 MPa. Pressure jumps can be performed as quickly as 5 ms, both with increasing and decreasing pressures. Pressure is generated by a motorized high pressure pump, and the system is controlled remotely via a graphical user interface to allow operation by a broad user base, many of whom may have little previous experience of high pressure technology. Samples are loaded through a dedicated port allowing the x-ray windows to remain in place throughout an experiment; this facilitates accurate subtraction of background scattering. The system has been designed specifically for use at beamline I22 at the Diamond Light Source, United Kingdom, and has been fully integrated with the I22 beamline control systems.

Dual-mode operation of flexible piezoelectric polymer diaphragm for intracranial pressure measurement

Abstract: The dual-mode operation of a polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) piezoelectric polymer diaphragm, in a capacitive or resonant mode, is reported as a flexible intracranial pressure (ICP) sensor. The pressure sensor using a capacitive mode exhibits a higher linearity and less power consumption than resonant mode operated pressure sensor. In contrast, the latter provides better sensitivity and easier adaption for wireless application. The metrological properties of the dual-mode ICP sensor being described are satisfactory in vitro. We propose that the piezoelectric polymer diaphragm has a promising future in intracranial pressure monitoring.

Continuous cuffless blood pressure monitoring based on PTT

Abstract: Blood pressure (BP) is one of the important vital signs that need to be monitored for personal healthcare. This paper describes the method developed by the authors to measure systolic blood pressure from pulse transit time (PTT) Pulse transit time is the time taken for the arterial pulse pressure wave to travel from the aortic valve to a peripheral site. It is usually measured from the R wave on the electrocardiogram to a photoplethysmography signal. PTT is inversely proportional to blood pressure. This method does not require an air cuff and only a minimal inconvenience of attaching electrodes and LED/photo detector sensors on a subject. Twenty three healthy subjects (age 18–60 yrs) were studied. Blood pressure measurement is carried out using pulse transit time and is compared with sphygmomanometry, the reference standard and the oscillometric based automatic BP measuring machine. The results show that the standard deviation of their differences was around 3 mmHg. The developed pulse transit time based method can be used as a noninvasive and cuffless alternative to the conventional occluding-cuff approaches for long-term and continuous monitoring of blood pressure.

Reservoir architecture and connectivity analysis

Abstract: An interactive system and method of operating the system to define and evaluate a model of a hydrocarbon reservoir. The reservoir model is defined from extrinsic information such as seismic surveys, well logs, and the like, and is based on elements of formation regions, connections among the regions, wells, and perforations. A boundary-element method is used to determine pressure interference responses, corresponding to the pressure at a perforation in response to a single perforation producing fluid at a unit flow rate. These pressure interference responses are then convolved with measured well flow rates obtained during production to arrive at estimates of the wellbore pressure at one or more wells of interest. The estimated wellbore pressure can be compared with downhole pressure measurements to validate the reservoir model, or to provoke the user into modifying the model and repeating the evaluation of the model.

Research on the mechanics of underwater supersonic gas jets

Abstract: An experimental research was carried out to study the fluid mechanics of underwater supersonic gas jets. High pressure air was injected into a water tank through converging-diverging nozzles (Laval nozzles). The jets were operated at different conditions of over-, full- and under-expansions. The jet sequences were visualized using a CCD camera. It was found that the injection of supersonic air jets into water is always accompanied by strong flow oscillation, which is related to the phenomenon of shock waves feedback in the gas phase. The shock wave feedback is different from the acoustic feedback when a supersonic gas jet discharges into open air, which causes screech tone. It is a process that the shock waves enclosed in the gas pocket induce a periodic pressure with large amplitude variation in the gas jet. Consequently, the periodic pressure causes the jet oscillation including the large amplitude expansion. Detailed pressure measurements were also conducted to verify the shock wave feedback phenomenon. Three kinds of measuring methods were used, i.e., pressure probe submerged in water, pressure measurements from the side and front walls of the nozzle devices respectively. The results measured by these methods are in a good agreement. They show that every oscillation of the jets causes a sudden increase of pressure and the average frequency of the shock wave feedback is about 5–10 Hz.

High-Frequency Pressure Measurements for Unstart Detection in Scramjet Isolators

Abstract: This paper describes an experimental investigation using an array of high-frequency pressure transducers located in the isolator/combustor region of a direct-connect hydrocarbon-fueled, scramjet combustor. Isolator/combustor entrance conditions were fixed and representative of a Mach-5.5 flight condition. Mean, standard deviation, and spectral content of measured pressures were similar to those measured in previous studies. A simple model relating the sum of measured pressures and the fuel flow rate delivered to the primary injectors was developed. Pressure measurements were post-processed and evaluated for use in a shock-position-control sensor to detect engine unstart. Four methods of post-processing the pressure data and corresponding detection criteria were evaluated: a) 150% pressure rise, b) 150% increase in standard deviation, c) 150% increase in power spectral density (PSD), and d) summation of pressures. Pressure summation typically provided 1 – 2 s more lead time in detecting unstart then any other method.

Optofluidic pressure sensor based on interferometric imaging.

Abstract: We present a chip-scale optofluidic interferometric sensor for measuring liquid pressure based on an imaging method. The chip was constructed with a polymer by multilayer soft lithography. It consists of a flexible air gap optical cavity, which, upon illumination by monochromatic light, generates interference patterns that depend on pressure. The pressure was measured by imaging and analyzing the interference patterns. We also employed a pattern recognition algorithm that significantly simplified the calculation and enhanced the measurement reliability. This pressure sensor was demonstrated with a working range of 0-22 psi and an accuracy of ±1.4% of full scale when temperature stabilized.

Pressure calculation in hybrid particle-field simulations

Abstract: In the framework of a recently developed scheme for a hybrid particle-field simulation techniques where self-consistent field (SCF) theory and particle models (molecular dynamics) are combined [J. Chem. Phys. 130, 214106 (2009)], we developed a general formulation for the calculation of instantaneous pressure and stress tensor. The expressions have been derived from statistical mechanical definition of the pressure starting from the expression for the free energy functional in the SCF theory. An implementation of the derived formulation suitable for hybrid particle-field molecular dynamics-self-consistent field simulations is described. A series of test simulations on model systems are reported comparing the calculated pressure with those obtained from standard molecular dynamics simulations based on pair potentials.

A micro-machined Pirani gauge for vacuum measurement of ultra-small sized vacuum packaging

Abstract: Quite a few MEMS devices need vacuum packaging technology to guarantee the desirable performance. Developing an absolute vacuum environment for those devices is indispensable. However, it is difficult to monitor the pressure change in vacuum chamber in on-line and real-time mode. A surface micro-machined Pirani gauge for measuring vacuum pressure inside vacuum packaging in wafer level was presented in this paper. It was designed with a simplified structure and did not need complex circuit. Only a simple Wheatstone bridge circuit is needed, which could be manufactured by conventional CMOS processes. Preliminary tests on this device were conducted. The experimental results show that the Pirani gauge is capable of measuring pressures from atmospheric value to 1 Pa and has a very good linearity in the range from1 Pa to 300 Pa. It demonstrates that the micro-machined Pirani gauge has great potential to be used in wafer level vacuum packaging. Also, the Pirani gauge is able to be the packaging hermeticity detector.

Location determination using radio wave measurements and pressure measurements

Abstract: A method and apparatus for determining a location of a wireless device using radio waves and pressure measurements is disclosed. In one embodiment, a plurality of Radio Signal Strength (RSS) measurements are used to trilaterate an approximate location of the wireless device. The wireless device also takes pressure measurements that are compared with a second pressure measurement made by at least one other pressure sensor at a known elevation and in a local area near the wireless device. This comparison is used to generate an accurate estimate of the elevation of the wireless device. The accurate estimate of elevation may be combined with the RSS measurements to yield an accurate estimate of the location of the wireless device.

Optical fiber Fabry-Perot pressure sensor and fabrication method thereof

Abstract: The invention relates to a novel optical fiber Fabry-Perot pressure sensor and a fabrication method thereof. The optical fiber Fabry-Perot pressure sensor is used for detecting the relative pressure and absolute pressure of liquid and gas as well as sound wave signals, ultrasonic wave signals and the like. The structure of the optical fiber Fabry-Perot pressure sensor mainly comprises an optical fiber, an elastic diaphragm, a sensor body and a miniature spring. Two methods and an alternative method can be adopted to form a Fabry-Perot cavity and fabricate the sensor. The elastic diaphragm and the sensing optical fiber are tightly contacted in a plane-sphere point contact manner; when the outside pressure is changed to cause the deformation of the elastic diaphragm, the diaphragm can drive the optical fiber to axially move in the sensor body, so that the length of the Fabry-Perot cavity of the optical fiber is changed; after a broadband light source is connected, by scanning the spectrum of the light passing through the optical fiber Fabry-Perot pressure sensor or extracting low-coherence interference fringes, the change of the cavity length can be extracted, and thereby pressure information can be obtained. The structure can avoid the defect that the diaphragm of the conventional optical fiber Fabry-Perot pressure sensor cannot be over-deformed, and can obtain higher measurement precision.

Aeroacoustic Investigation of a Single Airfoil Tip Leakage Flow

Abstract: Combined near and far field aeroacoustic measurements have been carried out during an original laboratory scale low Mach number (0‐0.3) experiment about the tip leakage flow past a single non-rotating airfoil. Such measurements were made possible by the use of a single airfoil located in the potential core of an open jet flow in the anechoic wind tunnel of the Ecole Centrale de Lyon. The airfoil was mounted between two flat plates. A strong tip clearance flow was achieved without rotation by paying a special attention to the choice of the airfoil which was a 5% camber, 10% thickness NACA5510 airfoil that provided a high lift at a 15° angle of attack. The experiment gave rise to an extensive data set obtained with several flow velocity measurement techniques (HWA, LDA, PIV), steady and unsteady pressure measurements on the airfoil and the casing plate as well as far field pressure measurements. Further, cross-analyses of various velocity and pressure signals allowed to locating sources and identifying their mechanisms. Results showed evidence of two components of tip leakage broadband self noise.