Differential Pressure Measurements Research Articles

P042: Pilot study for the inter-arm blood pressure systematic measurement during the diagnosis of transient ischemic attack in the emergency department

Introduction: Our principal aim was to document the feasibility of the systematic measurement of the inter-arm blood pressure difference (IABPD) during an episode of transient ischemic attack (TIA) or mild stroke diagnosed in the Emergency Department (ED). As secondary goal was to compare the systolic blood pressure (BP) at triage with the systolic BPs measured during the IABPD. Methods: This is a single center pilot study. Patients presenting in the ED for a diagnosis of TIA were recruited. Once patient has been triaged and diagnosed of TIA, a research assistant made sure that the patient lay on a stretcher for at least 5 minutes. Two automated sphygmomanometers were applied, on each arm. No specific device or device calibration were required. Three consecutive simultaneous BP readings were performed, inverting cuffs arm to arm between each reading. Only the last two set of readings were used to calculate the mean IABPD. This method enables to minimize the error coming from the potential sphygmomanometers’ inaccuracies. Results: 32 patients were recruited from June to September 2017 and all had a successful IABPD measurement. Four patients had an IABPD >10 mmHg, varying from 1.5 to 13 mmHg when the left arm was higher and from 1 to 61 mmHg when the right arm was higher. Of the 22 patients where the triage BP arm side selection was recorded, only 11 were congruent with the arm presenting the highest BP during the IABPD measurement. Selecting of the arm with the highest BP value may better reflect cerebrovascular risk exposition. The mean systolic BP at triage was 159.3 mmHg (95%CI: 144.9-173.7) compared to144.8 mmHg (95%CI: 132.9-156.7) if the arm with the highest value during the IABPD measurement is selected and 142.4 mmHg (95%CI: 130.8-154.0) if the same arm as triage is selected. The p-value for these differences were 0.003 and 0.001 respectively. The patient which presented the IABPD of 61 mmHg, had a stroke 3 days after its ED visit which subsequently led to her death 10 days later. Conclusion: Our results show that the systematic IABPD measurement using a pragmatic approach in the ED is feasible and is ready to investigate its use in the context of a new TIA or mild stroke. This information may contribute to a better discrimination of the short-term risk of stroke and may help to diagnose acute aortic dissection, monitor more accurately BP during hyperacute stroke or estimate intracerebral hemorrhage risk if systemic thrombolysis is considered.

Numerical investigation on the effects of building configuration on discharge coefficient for a cross-ventilated dairy building model

To estimate the ventilation rate of buildings, the orifice equation with a fixed discharge coefficient (Cd) is often applied. However, values of Cd may be not a constant for the openings of naturally-ventilated dairy buildings. The main objective of this study was to investigate the influence of the building configurations on the Cd value. In addition, since the value of the pressure difference across the opening is crucial to the application of the orifice equation, another objective was to evaluate the accuracy of using the orifice plate method in pressure difference measurements. The investigations were carried out using computational fluid dynamics simulations. The results showed that applying the orifice plate method to measure the pressure drop could result in up to 18.9% relative error in estimates of Cd for the case with an opening ratio of 81.4%. Additionally, the value of Cd was found to be dependent on the opening ratio, the inlet opening position, and the inlet-to-outlet area ratio, but it was independent of the outlet opening position and the roof slope. It can be concluded that the Cd value should be specified according to the opening configurations in the application of the orifice equation.

An Arduino-based low cost device for the measurement of the respiration rates of fruits and vegetables

A modular device based on open source software was developed for the determination of the respiration rates of produce in a closed system. The advantages of this system include simplicity, adaptability and low cost. The respirometer allowed the continuous measurement of CO2 concentration, barometric and differential pressures, and temperature. With the data obtained it was possible to calculate the CO2 production rate and to predict the O2 consumption rate and the respiratory quotient of the product, without using an O2 sensor. To assess the function of the device, the O2 and CO2 respiration rates of three products were determined. The good agreement observed between the respiratory quotient and the differential pressure suggests the possibility of using the differential pressure data as a direct indicator of the respiratory quotient evolution. This data could also be useful for monitoring metabolic shifts.

Experimental measurements of the high-temperature oxidation of carbon fibers

We carried out laboratory experiments to study the decomposition of carbon fibers at high temperature and studied the material used in charring carbon phenolic ablators for planetary probe heatshields. Porous plug samples were exposed to controlled rates of molecular oxygen, carbon dioxide, and carbon monoxide at furnace-heated flow-tube reactor temperatures between 700 and 1500 K and pressures between 2000 and 6200 Pa. We used calibrated mass spectroscopy to make time-resolved quantitative measurements of decomposition products of the gases downstream of the test sample. Absolute and differential pressure measurements were used to determine the high-temperature permeability of the material and to monitor changes during material decomposition, and we characterized the microstructure of the porous sample using scanning electron microscopy. We found substantial carbon fiber oxidation for O2 flows, resulting in increasing CO/CO2 production ratios with increasing temperature. The CO2 was shown to react with carbon fibers following a Boudouard reaction at temperatures above 1200 K.

Full-Scale Measurements of Wind-Pressure Coefficients in Twin Medium-Rise Buildings

Wind pressure coefficients (Cp) are important values for building engineering applications, such as calculation of wind loads or wind-induced air infiltration and especially for tall buildings that are more susceptible to wind forces. Wind pressure coefficients are influenced by a plethora of parameters, such as building geometry, position on the façade, exposure or sheltering degree, and wind direction. On-site measurements have been performed on a twin medium-rise building complex. Differential pressure measurements have been employed in order to determine the wind pressure coefficients at various positions along the windward façades of the twin buildings. The measurements show that one building provides substantial wind shelter to its twin and the microclimatic effect is captured by the measured wind pressure coefficients. They also showed that the wind pressure coefficients vary significantly spatially along the windward façades of the medium-rise buildings. Furthermore, the pressure measurements showed that the wind pressure coefficients fluctuate significantly during the measuring period. The use of the fluctuating Cp values by means of probability distribution function (pdf) for the calculation of air infiltration has been evaluated. The results indicate that the air flows deriving using fluctuating Cp values are more accurate than the ones calculated by the conventional method of using mean Cp values.

Pressure artifacts at isothermal operation of a metal hydride tank

The paper presents the results of experimental investigations on hydrogen absorption and desorption in the metal hydride reactor RS-1 containing 81 kg of La0.5Nd0.5Al0.1Fe0.4Co0.2Ni4.3 intermetallic compound at 60 °C isothermal conditions. During the reactor-scale measurements of pressure-composition isotherms we observe pressure artifacts; pressures for absorption are higher and for desorption are lower than equilibrium pressures obtained after cooling down and reheating of the reactor. This thermal relaxation procedure removes the pressure artifacts. The observed effect is similar to the large aliquot effect, and mostly affects the desorption isotherm. The highest measured pressure difference is 0.7 bar (11%).

Wet gas over-reading correction for ultrasonic flow meters

Oil and gas operators rely on accurate flow rate measurements to optimize production and generate more from their reservoirs, particularly in wet gas fields. A cost-effective solution for these flow measurements is the use of single-phase measurement technologies with an over-reading correction that corrects the gas flow rate for the presence of the liquid phase. Traditional flow measurement technologies in wet gas fields are Venturi meters and orifice plate meters that involve differential pressure measurements. Over the years, a higher installed base of ultrasonic flow meters is observed in wet gas fields. Ultrasonic flow meters have advantages over conventional wet gas technologies; however, an over-reading correction method for this measurement technology has not yet been derived. The current work is a first attempt to devise a correction method based on a large data set of ultrasonic measurements in horizontal configuration at conditions comparable to field applications. The correction method is a physical model for the gas void fraction and is based on the dominant dimensionless numbers in wet gas flows that originate from the fundamental equations of multiphase flow dynamics. This approach leads to the definition of the over-reading correction in different flow regimes in terms of these dimensionless numbers and is supported by an extensive set of measurement data and evidence from visual observation of the flow patterns. The correction method is capable of correcting the ultrasonic over-reading with a resulting uncertainty of about 4% for a 95% confidence interval for a range of conditions relevant to the oil and gas industry.

Silicon Nanoparticles with a Polymer-Derived Carbon Shell for Improved Lithium-Ion Batteries: Investigation into Volume Expansion, Gas Evolution, and Particle Fracture

Silicon (Si) and composites thereof, preferably with carbon (C), show favorable lithium (Li) storage properties at low potential, and thus hold promise for application as anode active materials in the energy storage area. However, the high theoretical specific capacity of Si afforded by the alloying reaction with Li involves many challenges. In this article, we report the preparation of small-size Si particles with a turbostratic carbon shell from a polymer precoated powder material. Galvanostatic charge/discharge experiments conducted on electrodes with practical loadings resulted in much improved capacity retention and kinetics for the Si/C composite particles compared to physical mixtures of pristine Si particles and carbon black, emphasizing the positive effect that the core–shell-type morphology has on the cycling performance. Using in situ differential electrochemical mass spectrometry, pressure, and acoustic emission measurements, we gain insights into the gassing behavior, the bulk volume expansion, and the mechanical degradation of the Si/C composite-containing electrodes. Taken together, our research data demonstrate that some of the problems of high-content Si anodes can be mitigated by carbon coating. Nonetheless, continuous electrolyte decomposition, particle fracture, and electrode restructuring due to the large volume changes during battery operation (here, ∼170% in the voltage range of 600–30 mV vs Li+/Li) remain as serious hurdles toward practical implementation.

On-line rheological characterization of semi-solid formulations

The rheological profile of a semi-solid product is a critical quality attribute. To monitor changes of this attribute during manufacturing, it would be beneficial to measure the rheological parameters in an on-line or in-line mode and implement this as a part of a control strategy for manufacturing of semi-solids. None of the process analytical technology (PAT) tools for measuring the rheological parameters have yet been widely accepted in the pharmaceutical area, as most of the equipment can only measure viscosity. Therefore, an automated system based on the measurement of pressure difference across both a topology optimized channel and a tube geometry (capillary viscometer) was investigated. The Pressure Difference Apparatus (PDA) can sample from the bulk intermediate/product stream and press the sample through the apparatus at different flow rates to yield a frequency sweep (G′ and G″) and a flow curve (viscosity). A calibration model was successfully prepared and verified with hydroxyethyl cellulose gels with polymer content varying from 1.0 to 1.5% (w/w) resulting in gels of different viscosities. The calibration model was used on-line during manufacturing of a gel and manufacturing changes related to dilution of the product were clearly reflected in the batch evolution profiles. The measurements with the PDA reflected the shear rate and frequency ranges relevant for manufacturing and thereby complemented the rheology measurements obtained with a standard rheometer with real time data.

Bioinspired wind field estimation—part 1: Angle of attack measurements through surface pressure distribution

One of the major challenges of Mini-Unmanned Aerial Vehicle flight is the unsteady interaction with turbulent environment while flying in lower levels of atmospheric boundary layer. Following inspiration from nature we expose a new system for angle of attack estimation based on pressure measurements on the wing. Such an equipment can be used for real-time estimation of the angle of attack during flight or even further building of wind velocity vector with additional equipment. Those information can find purpose in control and stabilization of the aircraft due to inequalities seen by the wing or even for various soaring strategies that rely on active control for energy extraction. In that purpose, flying wing aircraft has been used with totally four span-wise locations for local angle of attack estimation. In-flight angle of attack estimation from differential pressure measurements on the wing has been compared with magnetic sensor with wind vane. The results have shown that pressure ports give more reliable estimation of angle of attack when compared to values given by wind vane attached to a specially designed air-boom. Difference in local angle of attack at four span-wise locations has confirmed spatial variation of turbulence in low altitude flight. Moreover, theoretical law of energy dissipation for wind components described by Kaimal spectrum has shown acceptable match with estimated ones.

SAG foam flooding in carbonate rocks

Foam is used in gas-injection EOR processes to reduce the mobility of gas, resulting in greater volumetric sweep. SAG (Surfactant Alternating Gas) is a preferred method of injection as it results in greater injectivity in the field, but designing a successful process requires knowledge of foaming performance at very high foam qualities (gas fractional flows).Here the use of foam in low-permeability (∼1 mD) Indiana Limestone cores for SAG foam applications is studied. Coreflood experiments were performed for a range of foam qualities at high pressure (100 bar), elevated temperature (55 °C), high salinity (200,000 ppm) and in the presence of crude oil. The effectiveness of the foam was studied by differential pressure measurements along the core. Foam was still able to form under these stringent conditions, but it was a relatively weak foam (i.e. its ability to reduce gas mobility is modest). For one surfactant formulation, further analysis of the experimental results show that the foam would be able to maintain mobility control over the displaced phase, thus providing a stable displacement front, and that it can be used in a SAG foam process in these formations. For a second formulation the non-monotonic nature of the fractional-flow data requires further investigation before scale-up to the field.In addition, further coreflood experiments were carried out using heterogeneous, vuggy Edwards White cores with even lower permeability (∼0.5 mD). These experiments were performed to determine whether foaming is possible in heterogeneous media and especially to investigate the effects of disconnected vugs on the foaming performance. CT scans were taken during the period of foam injection to determine saturation profiles within the core. Foam was able to form inside these cores, but inside the vugs segregation was observed with liquid pockets visible in the bottom of the vugs and gas in the remainder. This segregation was only a local effect though, confined to the vug itself, and foam was able to persist in the rest of the core.

Modelling of the monitoring and control system of extraction units with nuclear-safe tanks via use of capillary impulse lines with differential low-pressure gages

This paper focuses on the computer-aided simulation of extraction process in the cascade of reverse-flow centrifugal extractors with nuclear-safe tanks. The major objective of this work is to design an advanced control system for enhancement of extracting technology efficiency. The basis of the monitoring and control system is that the systems should be based on non-destructive measuring techniques. Two models of monitoring systems are being considered: the measuring system in nuclear-safe tanks where capillary impulse lines are used for measurement of differential pressure at various points in the process media, and model of spectrometric system. The density measurement in both presented systems is indirect. The experimental studying of monitoring spectrometric system have shown that the accuracy of experimental data less than 1 % in steady-state condition and more than 3 % in a dynamic one. The accuracy degradation is due to air bubbles presents in the solvent stream.

Investigation of the flow patterns produced from sudden expansion geometries using pressure difference measurements and flow visualisation techniques

The aim of this study was to investigate the flow behaviour produced from inward sudden and outward expansion geometries. A flow apparatus made of Perspex has been used to measure the variations of pressure differences, and to observe the visualised flow streams, downstream of the expansions. For the outward expansion, the pressure measurements showed two types of oscillations: low frequencies at around 1Hz and high frequencies at around 10Hz. The oscillations at low frequencies have been found to be more dominant and related to the precession of the air flow. Further pressure measurements, together with the visualisation results, showed that this precessing behaviour was stronger near the wall of the expansion chamber. In comparison, the pressure measurements in the inward expansion showed higher overall flow stability. Measurements at different radial distances showed that the low-frequency precessing behaviour appeared to be confined to the central area of the chamber (33–50% diameter from the radial centre). This precession has been found to have a small influence on the flow field near the chamber wall, which may contribute to the flow stability. This finding was also supported by the visualisation results. A swirl module has also been used to investigate the effects of inlet swirl angle on the air flow pattern, where the pressure measurements showed no apparent changes in the overall flow behaviour, but a reduction has been observed in the dominance of the low-frequency oscillations and an increase in the frequencies of the high-frequency oscillations. Flow visualisation of the swirler case showed that the precessing eddies started dissipation at a shorter distance from the expansion point. This study showed the close relationship between the flow behaviours and the geometries of the inlet expansions, and possibility of controlling the flow behaviours by design features such as swirler modules. Such findings are valuable to processes such as spray-drying, which require both sufficient mixing and flow stability. The study also illustrated the use of flow visualisation techniques as complimentary tools to assess complex flow behaviour.

NPP main feedwater flow Venturi tube erosion characteristics study and improvement

The main feedwater flow of nuclear power units is mainly measured according to Venturi tube differential pressure measurement philosophy. However Venturi tube is subject to fluid erosion and its characteristics will change, directly affecting the measurement accuracy of main feedwater flow which is an important process parameter for nuclear power units. It analyzes the fluid erosion phenomenon of NPP Venturi tubes based on the main feedwater flow measurement data and operation experience of several nuclear power units in many years, and gives erosion characteristic formulas and erosion characteristic curves. In addition, this paper provides improvement solutions in the aspects of differential pressure correction, replacement criteria establishment, design improvement (in selection of high erosion resistance material for internal passage and improvement of construction strength of weak parts) and real-time monitoring of flow data during power operation. These solutions have been verified on site and found feasible and effective.

Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

When low-salinity water containing sulfate ions is injected into carbonate reservoirs, rock dissolution and in situ precipitation occur, altering rock permeability and wettability. Particularly, when barium ions are present in formation water, they react chemically with {text{SO}}_{4}^{2 - }, and BaSO4 is precipitated. These reactions can cause a serious impact on the efficiency of enhanced oil recovery (EOR). Therefore, the main purpose of this study was to identify EOR efficiency induced by low-salinity waterflooding (LSWF) when Ba2+ is present in carbonate reservoirs. From the experimental results, it was confirmed that the permeability calculated by the measured pressure difference was improved because of rock dissolution predominating over in situ precipitation for the case of low Ba2+ concentrations. In the analysis of wettability alteration through the measurements of relative permeabilities before and after LSWF, the higher Ba2+ concentration case consumed more {text{SO}}_{4}^{2 - } in precipitating the BaSO4, resulting in weaker wettability alteration due to the reduction of sulfate activity. These phenomena ultimately influenced EOR efficiency, i.e., the oil recovery was greater for the lower Ba2+ concentration.

Mathematical modeling of optical MEMS differential pressure sensor using waveguide Bragg gratings embedded in Mach Zehnder interferometer

This paper presents theoretical analysis of a silicon based micro-machined differential pressure sensor using a square shaped clamped diaphragm and surface relief waveguide Bragg gratings embedded in a Mach Zehnder interferometer (MZI). Each of the arms of the MZI has one surface relief Bragg grating embedded in it. Each grating is mounted at the edge of a micro-machined diaphragm so as to obtain maximum stress. Coupled mode theory has been used to design the directional coupler to equally couple the light into both of the arms of MZI and also to design and analyse the shifts in the wavelengths of the Bragg gratings due to applied pressures. The wavelength shift difference of the two gratings gives the differential pressure sensitivity and also eliminates the noise due to temperature variation. Simulation results indicate that the differential pressure measurement sensitivity is 0.2 pm/Pa.

Experimental study on the in vivo continuous measurement of pressure difference between the anterior and the posterior chambers

A set of device for the in vivo measurement of the pressure difference between the anterior and the posterior chambers (PDAP) was designed to investigate the temporal varying rules of PDAP in the anterior segment of rabbit eyes. A platform was established for the in vivo measurement of PDPA according to the mechanism of joint implement. Rabbit models with high intraocular pressure (IOP) were constructed by means of injecting Carbomer into anterior chamber to increase IOP. The in vivo 24 hours continuous measurements of PDAP were performed for normal rabbit eye and eye with high IOP. The developed device could sensitively response to the small pressure difference in eye. The pressure difference in the normal rabbit eye varied with time, and the variation range during a whole day was 5.84-96.84 Pa which reflected the existence of physiological rule. For the rabbit eye with high IOP, pressure in anterior chamber was higher than that in posterior chamber which was in consistence with the theory of self-adaptation adjustment. The present study indicates that the approaches and device designed in this paper can well implement the measurement of PDAP as well as the temporal varying rules of PDAP in the anterior segment during a whole day.

Evaluation оf the Protective Properties of Filtering Half-Masks by Measuring Pressure Difference

Evaluation оf the Protective Properties of Filtering Half-Masks by Measuring Pressure Difference

Evaluation оf the Protective Properties of Filtering Half-Masks by Measuring Pressure Difference

Evaluation оf the Protective Properties of Filtering Half-Masks by Measuring Pressure Difference

A silicon rectangular micro-orifice for gas flow measurement at moderate Reynolds numbers: design, fabrication and flow analyses

This work describes a micro-flowmeter for moderate flow rates of gases based on a differential pressure measurement. The micro-flowmeters consist of a microfabricated silicon–glass rectangular micro-orifice plate, with external pressure measurement. We experimentally evaluate the effects of geometrics parameters, Reynolds number and compressibility on the discharge coefficient. The paper examines a series of 13 rectangular micro-orifice sizes, with orifice hydraulic diameters ranging from 115 to 362 µm. The behavior of the discharge coefficient is presented for orifice Reynolds numbers ranging from 200 to 18000. Agreement is shown between the experimental and numerical results of the discharge coefficient. The micro-flowmeters measure moderate flow of air ranging from 1 to 106 mg/s. This demonstration implements a design method of micro-flowmeters that can be used in a broad range of microfluidic applications, such as microreactors and power MEMS.