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Van Zante, D. E., K. L. Suder, A. J. Strazisar et T. H. Okiishi. « An Improved Aspirating Probe for Total-Temperature and Total-Pressure Measurements in Compressor Flows ». Journal of Turbomachinery 117, no 4 (1 octobre 1995) : 642–49. http://dx.doi.org/10.1115/1.2836583.
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The aspirating probe originally designed by Epstein and Ng at MIT was modified by replacing the two platinum-coated tungsten hot wires normally used with platinum–iridium alloy wires. The resulting improved unsteady total pressure and total temperature resolution of the modified probe is demonstrated. Flowfield measurements were made downstream of NASA Rotor 37 for a part-speed operating condition to test the performance of the probe. Time-resolved blade-to-blade total temperature and total pressure as calculated from the two platinum–iridium hot-wire voltages are shown. The flowfield measurements are compared with independent measurements of total pressure with high response transducers and total temperature calculated from laser anemometer measurements. Limitations of a more often used unsteady temperature data reduction method, which involves only one aspirating probe hot-wire voltage and a high-response pressure measurement, are discussed.
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Ng, Wing-Fai, et Joel C. Rosson. « Cryogenic tunnel measurement of total temperature and pressure ». Journal of Aircraft 23, no 3 (mars 1986) : 244–49. http://dx.doi.org/10.2514/3.45296.
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Buttsworth, D. R., T. V. Jones et K. S. Chana. « Unsteady Total Temperature Measurements Downstream of a High-Pressure Turbine ». Journal of Turbomachinery 120, no 4 (1 octobre 1998) : 760–67. http://dx.doi.org/10.1115/1.2841787.
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An experimental technique for the measurement of flow total temperature in a turbine facility is demonstrated. Two thin film heat transfer gases located at the stagnation point of fused quartz substrates are operated at different temperatures in order to determine the flow total temperature. With this technique, no assumptions regarding the magnitude of the convective heat transfer coefficient are made. Thus, the probe can operate successfully in unsteady compressible flows of arbitrary composition and high free-stream turbulence levels without a heat transfer law calibration. The operation of the total temperature probe is first demonstrated using a small wind tunnel facility. Based on results from the small wind tunnel tests, it appears that the probe total temperature measurements are accurate to within ±1 K. Experiments using the probe downstream of a high-pressure turbine stage are than described. Both high and low-frequency components of the flow total temperature can be accurately resolved with the present technique. The probe measures a time-averaged flow total temperature that is in good agreement with thermocouple measurements made downstream of the rotor. Frequencies as high as 182 kHz have been detected in the spectral analysis of the heat flux signals from the total probe. Through comparison with fast-response aerodynamic probe measurements, it is demonstrated that the current measurement location, the total temperature fluctuations arise mainly due to the isentropic extraction of work by the turbine. The present total temperature probe is demonstrated to be an accurate, robust, fast-response device that is suitable for operation in a turbomachinery environment.
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Mersinligil, M., J. Desset et J. F. Brouckaert. « High-temperature high-frequency turbine exit flow field measurements in a military engine with a cooled unsteady total pressure probe ». Proceedings of the Institution of Mechanical Engineers, Part A : Journal of Power and Energy 225, no 7 (29 septembre 2011) : 954–63. http://dx.doi.org/10.1177/0957650911413697.
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The measurement of unsteady pressures within the hot components of gas turbine engines still remains a true challenge for test engineers. Several high-temperature pressure sensors have been developed, but so far, their applications are restricted to unsteady wall static pressure measurements. Because of the severe flow conditions such as turbine inlet temperatures of 1700 °C and pressures of 50 bar or more in the most advanced aero-engine designs, few (if any) experimental techniques exist to measure the time-resolved flow total pressure inside the gas path. This article describes the measurements performed at the turbine exit of a military engine with a cooled fast response total pressure probe. The probe concept is based on the use of a conventional miniature piezo-resistive pressure sensor, located in the probe tip to achieve a bandwidth of at least 40 kHz. Due to the extremely harsh conditions, the probe and sensor are heavily water cooled. The probe was designed to be continuously immersed into the hot gas stream to obtain time series of pressure with a high bandwidth and therefore statistically representative average fluctuations at the blade passing frequency (BPV). The experimental results obtained with a second-generation prototype are presented. The probe was immersed into the engine through the bypass duct between turbine exit and flame-holders of the afterburner of a Volvo RM12 engine, at exhaust temperatures above 900 °C. The probe was able to resolve the BPV (∼17 kHz) and several harmonics up to 100 kHz.
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Zheng, Guanghua, Fei Shui, Jinxin Hu, Xin Liu et Huazhong Xiao. « Effects of probes with different structures on the flow field and measurement results of imported compressors ». Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, no 4 (août 2021) : 858–64. http://dx.doi.org/10.1051/jnwpu/20213940858.
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In this paper, the measurement accuracy of two different types of total pressure probe and total temperature probe in turboshaft engine compressor inlet channel and the influence of these two probes on the flow field through numerical simulation was studied. At the same time, the influence of the probe structure and installation position on probe measurement results under three typical working conditions of cruise, maximum continuous and takeoff was analyzed. The simulation results showed that the higher the engine inlet flow rate, the greater the measurement error of the probe. Comparing with the total temperature probe, the total pressure probe measurement accuracy is more influenced by the flow rate. The velocity uniformity is less affected by the engine operating conditions and is mainly related to the structure of the inserted probes. The closer the total pressure probe to the support plate, the greater the measurement error. The probe installation position has a small effect on the total pressure loss coefficient at the outlet.
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Kreher, K., G. E. Bodeker et M. Sigmond. « An objective determination of optimal site locations for detecting expected trends in upper-air temperature and total column ozone ». Atmospheric Chemistry and Physics Discussions 15, no 2 (19 janvier 2015) : 1617–50. http://dx.doi.org/10.5194/acpd-15-1617-2015.
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Abstract. In the first study reported on here, requirements on random uncertainty of instantaneous temperature measurements, sampling frequency, season and pressure, required to ensure a minimum random uncertainty of monthly mean temperatures, have been explored. These results then inform analyses conducted in a second study which seeks to identify the optimal location of sites for detecting projected trends in upper-air temperatures in the shortest possible time. The third part of the paper presents a similar analysis for the optimal locations of sites to detect projected trends in total column ozone. Results from the first study show that only for individual measurement random uncertainties > 0.2 K does the measurement random uncertainty start to contribute significantly to the random uncertainty of the monthly mean. Analysis of the effects of the individual measurement random uncertainty and sampling strategy on the ability to detect upper-air temperature trends shows that only when the measurement random uncertainty exceeds 2 K, and measurements are made just once or twice a month, is the quality of the trend determination compromised. The time to detect a trend in some upper-air climate variable is a function of the unforced variance in the signal, the degree of autocorrelation, and the expected magnitude of the trend. For middle tropospheric and lower stratospheric temperatures, the first two quantities were derived from Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit (AMSU) measurements while projected trends were obtained by averaging 21st century trends from simulations made by 11 chemistry–climate models (CCMs). For total column ozone, variance and autocorrelation were derived from the Bodeker Scientific total column ozone database with projected trends obtained from median values from 21 CCM simulations of total column ozone changes over the 21st century. While the optimal sites identified in this analysis for detecting temperature and total column ozone trends in the shortest time possible result from our use of only one of a wide range of objective strategies, these results provide additional incentives for initiating measurement programmes at these sites or, if already in operation, to continue to be supported.
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Balla, R. Jeffrey, Matthew N. Rhode et Joel L. Everhart. « Supersaturation Total Temperature, Pitot Pressure, and Rayleigh Scattering Measurements at Mach 10 ». AIAA Journal 52, no 7 (juillet 2014) : 1452–65. http://dx.doi.org/10.2514/1.j052608.
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Rocha, Hermes S. da, Patricia A. A. Marques, Antonio P. de Camargo, Douglas L. dos Reis, Eric A. da Silva et José A. Frizzone. « Dripper testing : Application of statistical quality control for measurement system analysis ». Revista Brasileira de Engenharia Agrícola e Ambiental 21, no 9 (septembre 2017) : 587–93. http://dx.doi.org/10.1590/1807-1929/agriambi.v21n9p587-593.
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ABSTRACT Laboratory tests for technical evaluation or irrigation material testing involve the measurement of many variables, as well as monitoring and control of test conditions. This study, carried out in 2016, aimed at using statistical quality control techniques to evaluate results of dripper tests. Exponentially weighted moving average control charts were elaborated, besides capability indices for the measurement of the test pressure and water temperature; and study on repeatability and reproducibility (Gage RR) of flow measurement system using 10 replicates, in three work shifts (morning, afternoon and evening), with 25 emitters. Both the test pressure and water temperature remained stable, with “excellent” performance for the pressure adjustment process by integrative-derivative proportional controller. The variability between emitters was the component with highest contribution to the total variance of the flow measurements, with 96.77% of the total variance due to the variability between parts. The measurement system was classified as “acceptable” or “approved” by the Gage RR study; and non-random causes of significant variability were not identified in the routine of tests.
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Tomson, Mason B., Amy T. Kan, Gongmin Fu et Lili Cong. « Measurement of Total Alkalinity and Carboxylic Acid and Their Relation to Scaling and Corrosion ». SPE Journal 11, no 01 (1 mars 2006) : 103–10. http://dx.doi.org/10.2118/87449-pa.
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Summary Alkalinity is needed in many water-treatment calculations such as scale, corrosion, precipitation, and oxidation, yet the concept is often misunderstood. In natural waters, alkalinity often is not equal to bicarbonate concentration, because natural waters contain base-contributing anions that can significantly affect alkalinity. However, alkalinity is commonly assumed to be equal to the bicarbonate concentration in many scale- and corrosion-prediction algorithms. When other anions (e.g., carboxylates) are present, bicarbonate concentration in production tubing is not a conservative quantity; it varies with CO2 partial pressure, temperature, and carboxylate concentrations in a complicated manner up and down a well. Reliable methods to accurately measure true alkalinity are scarce, especially when multiple weak acids are present and the effects of TDS on electrode and color endpoint are significant. Oilfield brines contain aliphatic carboxylic acids of one to six carbons (e.g., acetate) up to 5000 mg/L. The highest concentrations of carboxylates tend to be in waters from reservoirs at temperatures of 80 to 100°C. In this paper, a new analytical procedure and computation routine to determine alkalinity and carboxylic acids simultaneously will be discussed. The procedure was recently debugged and simplified by the Rice U. Brine Chemistry Consortium (Rice BCC). The new titration method is based upon simultaneous analysis of the titration curve determined at fixed PCO2 and emphasizes the titration shape (profile) instead of the endpoint inflection as is done presently. A wide range of natural and synthetic waters has been tested. Excellent agreement was observed between the true and calculated carboxylic acid concentration with a correlation coefficient squared of 0.9986. Once the total alkalinity and acetic acid concentrations are determined, the theoretically correct bicarbonate concentration and/or pH at any given operation temperature or pressure can be calculated. The intricate interrelationship of total alkalinity, carboxylic acids, and pH on scale and corrosion will be discussed by using case studies.
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Lubbock, RJ, et MLG Oldfield. « Turbulent velocity and pressure fluctuations in gas turbine combustor exit flows ». Proceedings of the Institution of Mechanical Engineers, Part A : Journal of Power and Energy 232, no 4 (26 septembre 2017) : 337–49. http://dx.doi.org/10.1177/0957650917732885.
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This paper presents the results of two test programmes using novel instrumentation to characterise the pressure and turbulent velocity fields in gas-turbine combustor exit flows. The probes are uncooled, therefore a fast-insertion traverse system is employed to prevent thermal degradation of the instrumentation in these severely hostile high-temperature environments. High-bandwidth ultra-miniature pressure transducers are used to measure unsteady total pressure, whilst a Pitot tube is employed to measure time-averaged total pressure. The probes are 4 mm in diameter with a measurement bandwidth of the order of 100 kHz. In the first test programme, the probes are used to characterise the streamwise turbulent velocity field approximately two axial chords downstream of an uncooled single-stage turbine in a turbojet engine. Established data reduction methods and calibration against a hot-wire are used to obtain turbulent velocity fluctuations from unsteady total pressure measurements. Comprehensive turbulence results are presented including time-histories, power spectra, intensities, and lengthscales obtained at four-engine conditions and at two radial and two circumferential measurement locations. In the second test programme the probes are demonstrated in an industrial combustor rig, featuring a can combustor with swirler nozzle and no dilution holes, at temperatures up to 1500 K. Static pressure fluctuations are obtained up to 100 kHz, and some typical combustor spectral features are identified.
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Siasko, A., Yu Golubovskii, S. Pavlov, E. Dzlieva, L. Novikov, M. Golubev et V. Karasev. « About the measurement of electric field and electron temperature by the spectroscopic method in a gas mixture ». Physics of Plasmas 30, no 3 (mars 2023) : 033701. http://dx.doi.org/10.1063/5.0135329.
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The paper is dedicated to the advance of the spectroscopic method for measuring the electric fields and electron temperatures in a mixture of inert gases with significantly different excitation and ionization potentials. The method based on the measurement of the ratio of the spectral line intensities was applied to the Ne–Kr discharge. Plasma parameters were evaluated based on the solution of the non-local Boltzmann kinetic equation for the Ne–Kr mixture at low pressures and currents. Electric fields and electron temperatures were obtained as functions of the discharge current, total gas pressure, and density of the Kr admixture. The discharge current varied in the range from 1 to 5 mA, the pressure from 0.27 to 1 Torr, and the Kr admixture from 0.5% to 11% from the total gas pressure. The results demonstrate the possibility of using the described technique for diagnostics of dusty plasmas and other plasma objects operating on gas mixtures with significantly different excitation and ionization potentials.
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Weinstock, E. M., J. B. Smith, D. Sayres, J. R. Spackman, J. V. Pittman, N. Allen, J. Demusz et al. « Measurements of the Total Water Content of Cirrus Clouds. Part I : Instrument Details and Calibration ». Journal of Atmospheric and Oceanic Technology 23, no 11 (1 novembre 2006) : 1397–409. http://dx.doi.org/10.1175/jtech1928.1.
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Abstract This paper describes an instrument designed to measure the sum of gas phase and solid phase water, or total water, in cirrus clouds, and to be mounted in a pallet in the underbelly of the NASA WB-57 research aircraft. The ice water content of cirrus is determined by subtracting water vapor measured simultaneously by the Harvard water vapor instrument on the aircraft. The total water instrument uses an isokinetic inlet to maintain ambient particle concentrations as air enters the instrument duct, a 600-W heater mounted directly in the flow to evaporate the ice particles, and a Lyman-α photofragment fluorescence technique for detection of the total water content of the ambient air. Isokinetic flow is achieved with an actively controlled roots pump by referencing aircraft pressure, temperature, and true airspeed, together with instrument flow velocity, temperature, and pressure. Laboratory calibrations that utilize a water vapor addition system that adds air with a specific humidity tied to the vapor pressure of water at room temperature and crosschecked by axial and radial absorption of Lyman-α radiation at the detection axis are described in detail. The design provides for in-flight validation of the laboratory calibration by intercomparison with total water measured by radial absorption at the detection axis. Additionally, intercomparisons in clear air with the Harvard water vapor instrument are carried out. Based on performance of the Harvard water vapor instrument, this instrument has the detection capability of making accurate measurements of total water with mixing ratios in the mid- to upper troposphere of up to 2500 ppmv and mixing ratios in the lower stratosphere of about 5 ppmv, corresponding to almost three orders of magnitude in measurement capability.
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Hurst, D. F., E. G. Hall, A. F. Jordan, L. M. Miloshevich, D. N. Whiteman, T. Leblanc, D. Walsh, H. Vömel et S. J. Oltmans. « Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE 2009 ». Atmospheric Measurement Techniques Discussions 4, no 4 (11 juillet 2011) : 4357–401. http://dx.doi.org/10.5194/amtd-4-4357-2011.
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Abstract. We compare coincident, balloon-borne, in situ measurements of temperature and pressure by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and measurements of relative humidity (RH) by Vaisala RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with mixed payloads are analyzed in 1-km altitude bins to quantify measurement biases between sensors and how they vary with altitude. The disparities between sensors determined here are compared to measurement uncertainties quoted by the two radiosonde manufacturers. Our comparisons expose several flight profiles with anomalously large measurement differences. Excluding these anomalous profiles, 33 % of RS92-iMet median temperature differences exceed the uncertainty limits calculated from manufacturer-quoted uncertainties. A statistically significant, altitude-independent bias of about 0.5 ± 0.2 °C is revealed for the RS92-iMet temperature differences. Similarly, 23 % of RS92-iMet median pressure differences exceed the quoted uncertainty limits, with 83 % of these excessive differences above 16 km altitude. The pressure differences are altitude dependent, increasing from −0.6 ± 0.9 hPa at the surface to 0.7 ± 0.1 hPa above 15 km. Temperature and pressure differences between redundant RS92 sondes on the same balloon exceed manufacturer-quoted reproducibility limits 20 % and 2 % of the time, respectively, with most of the excessive differences belonging to anomalous difference profiles. Relative humidity measurements by RS92 sondes are compared to other RS92 sondes and to RH values calculated using frost point hygrometer measurements and coincident radiosonde temperature measurements. For some flights the RH differences are anomalously large, but in general are within the ±5 % RH measurement uncertainty limits quoted for the RS92. The quantitative effects of RS92 and iMet pressure and temperature differences on frost point-based water vapor mixing ratios and RH values, respectively, are also presented.
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Settembre, N., T. Kagayama, P. Kauhanen, P. Vikatmaa, Y. Inoue et M. Venermo. « The Influence of Heating on Toe pressure in Patients with Peripheral Arterial Disease ». Scandinavian Journal of Surgery 107, no 1 (18 mai 2017) : 62–67. http://dx.doi.org/10.1177/1457496917705994.
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Background and Aim: The toe skin temperature in vascular patients can be low, making reliable toe pressure measurements difficult to obtain. The aim of this study was to evaluate the effect of heating on the toe pressure measurements. Materials and Methods: A total of 86 legs were examined. Brachial pressure and toe pressure were measured at rest in a supine position using a laser Doppler device that also measured skin temperature. After heating the toes for 5 min with a heating pad, we re-measured the toe pressure. Furthermore, after heating the skin to 40° with the probe, toe pressures were measured a third time. Results: The mean toe skin temperature at the baseline measurement was 24.0 °C (standard deviation: 2.8). After heating the toes for 5 min with a warm heating pad, the skin temperature rose to a mean 27.8 °C (standard deviation: 2.8; p = 0.000). The mean toe pressure rose from 58.5 (standard deviation: 32) to 62 (standard deviation: 32) mmHg (p = 0.029). Furthermore, after the skin was heated up to 40 °C with the probe, the mean toe pressure in the third measurement was 71 (standard deviation: 34) mmHg (p = 0.000). The response to the heating varied greatly between the patients after the first heating—from −34 mmHg (toe pressure decreased from 74 to 40 mmHg) to +91 mmHg. When the toes were heated to 40 °C, the change in to toe pressure from the baseline varied between −28 and +103 mmHg. Conclusion: Our data indicate that there is a different response to the heating in different clinical situations and in patients with a different comorbidity.
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Pečinka, Jiří, Gabriel Thomas Bugajski, Petr Kmoch et Adolf Jílek. « JET ENGINE INLET DISTORTION SCREEN AND DESCRIPTOR EVALUATION ». Acta Polytechnica 57, no 1 (28 février 2017) : 22–31. http://dx.doi.org/10.14311/ap.2017.57.0022.
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Total pressure distortion is one of the three basic flow distortions (total pressure, total temperature and swirl distortion) that might appear at the inlet of a gas turbine engine (GTE) during operation. Different numerical parameters are used for assessing the total pressure distortion intensity and extent. These summary descriptors are based on the distribution of total pressure in the aerodynamic interface plane. There are two descriptors largely spread around the world, however, three or four others are still in use and can be found in current references. The staff at the University of Defence decided to compare the most common descriptors using basic flow distortion patterns in order to select the most appropriate descriptor for future department research. The most common descriptors were identified based on their prevalence in widely accessible publications. The construction and use of these descriptors are reviewed in the paper. Subsequently, they are applied to radial, angular, and combined distortion patterns of different intensities and with varied mass flow rates. The tests were performed on a specially designed test bench using an electrically driven standalone industrial centrifugal compressor, sucking air through the inlet of a TJ100 small turbojet engine. Distortion screens were placed into the inlet channel to create the desired total pressure distortions. Of the three basic distortions, only the total pressure distortion descriptors were evaluated. However, both total and static pressures were collected using a multi probe rotational measurement system.
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Martinerie, P., D. Raynaud, D. Mazaudier, A. J. Gow, G. Holdsworth, V. Ya Lipenkov et N. W. Young. « The Relationship Between Total Gas Content of Polar Ice, Atmospheric Pressure and Surface Elevation (Abstract) ». Annals of Glaciology 11 (1988) : 203. http://dx.doi.org/10.1017/s0260305500006613.
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The air found in polar ice becomes isolated from the atmosphere during the transformation of snow into ice. The total gas content, V, measured on selected ice samples depends theoretically on the atmospheric pressure and temperature prevailing at the ice-formation site and also on the volume, Vc, of the firn pores at the time they become isolated from the atmosphere in newly formed ice. In spite of scattered individual values, a clear decrease in mean v-results has previously been observed for increasing elevations at the ice-formation site. Assuming that the pores close off at atmospheric pressure, this decrease primarily reflects the pressure-elevation gradient and typically only about 10% of the decrease can be attributed to the temperature-elevation gradient or changes in Vc. Measurements of the total gas content of Antarctic ice cores are potentially the most direct and sensitive indicator of the elevation at which the ice was formed and provide a unique tool for reconstructing the past elevation of the ice-sheet surface. Nevertheless, to make such a reconstruction with confidence, we need first to evaluate the individual contributions of the different parameters which should influence Vc. Along this line, a stage was reached with the semi-empirical observation of a quasi-linear correlation between mean Vc and temperature, although the data points on which the correlation is based are relatively scarce. Furthermore, confidence in the paleo-interpretation of V-measurements is dependent also on an understanding of the scatter in individual V-values generally observed for a given ice-core section. New measurements of V are presented, which permit a better and more detailed description to be made of the changes in V with atmospheric pressure and elevation under approximately present-day conditions. As a first step, scattering in the values of individual V-measurements of a single core section is investigated. The experimental method used for this work is basically the same as the one used for establishing the relationship between V and elevation, as given by Raynaud and Lebel (1979). Generally measurements performed on the same horizontal layer (about 3 cm thick) reproduce the same result within the experimental uncertainty (which is ±1%). On the other hand, measurements performed on adjacent horizontal layers may show V-differences as high as 20-25%. This confirms that the variability of the V measurements that occurs over short intervals in the core is not due to experimental uncertainties and should mainly reflect changes in Vc. The main reason for making this new set of measurements was to increase significantly the number of sites investigated in the study of the relationship between V and elevation. The work of Raynaud and Lebel (1979) was based on six sites. The results for 14 sites (in Antarctica, Greenland, and on Mount Logan in Canada) are now available, with elevations ranging from about 340 to 5300 m and temperatures in the range −12.4° to −55.4 °C. The results confirm a general decrease in Vc with temperature. But at least one site shows mean V-values which are clearly incompatible with this general trend. Finally, before proceeding further with studies of the distribution of V versus site parameters, we need to correct our V-measurements for the loss of gas which occurs when cutting the ice samples (and consequently opening air bubbles at the sample surface). We have developed, for this purpose, a technique which calculates random distributions of bubbles in the samples and counts the cut bubbles. This calculation depends on bubble shape and size as well as on sample volume and V. In the case of the samples used in the present study, between 3 and 10% of gas is typically lost during cutting. Bubble-size measurements have yet to be made before an accurate correction can be applied to the measurements presented here.
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Martinerie, P., D. Raynaud, D. Mazaudier, A. J. Gow, G. Holdsworth, V. Ya Lipenkov et N. W. Young. « The Relationship Between Total Gas Content of Polar Ice, Atmospheric Pressure and Surface Elevation (Abstract) ». Annals of Glaciology 11 (1988) : 203. http://dx.doi.org/10.3189/s0260305500006613.
Texte intégralRésumé :
The air found in polar ice becomes isolated from the atmosphere during the transformation of snow into ice. The total gas content, V, measured on selected ice samples depends theoretically on the atmospheric pressure and temperature prevailing at the ice-formation site and also on the volume, Vc, of the firn pores at the time they become isolated from the atmosphere in newly formed ice.In spite of scattered individual values, a clear decrease in mean v-results has previously been observed for increasing elevations at the ice-formation site. Assuming that the pores close off at atmospheric pressure, this decrease primarily reflects the pressure-elevation gradient and typically only about 10% of the decrease can be attributed to the temperature-elevation gradient or changes in Vc.Measurements of the total gas content of Antarctic ice cores are potentially the most direct and sensitive indicator of the elevation at which the ice was formed and provide a unique tool for reconstructing the past elevation of the ice-sheet surface. Nevertheless, to make such a reconstruction with confidence, we need first to evaluate the individual contributions of the different parameters which should influence Vc. Along this line, a stage was reached with the semi-empirical observation of a quasi-linear correlation between mean Vc and temperature, although the data points on which the correlation is based are relatively scarce. Furthermore, confidence in the paleo-interpretation of V-measurements is dependent also on an understanding of the scatter in individual V-values generally observed for a given ice-core section.New measurements of V are presented, which permit a better and more detailed description to be made of the changes in V with atmospheric pressure and elevation under approximately present-day conditions. As a first step, scattering in the values of individual V-measurements of a single core section is investigated. The experimental method used for this work is basically the same as the one used for establishing the relationship between V and elevation, as given by Raynaud and Lebel (1979). Generally measurements performed on the same horizontal layer (about 3 cm thick) reproduce the same result within the experimental uncertainty (which is ±1%). On the other hand, measurements performed on adjacent horizontal layers may show V-differences as high as 20-25%. This confirms that the variability of the V measurements that occurs over short intervals in the core is not due to experimental uncertainties and should mainly reflect changes in Vc.The main reason for making this new set of measurements was to increase significantly the number of sites investigated in the study of the relationship between V and elevation. The work of Raynaud and Lebel (1979) was based on six sites. The results for 14 sites (in Antarctica, Greenland, and on Mount Logan in Canada) are now available, with elevations ranging from about 340 to 5300 m and temperatures in the range −12.4° to −55.4 °C. The results confirm a general decrease in Vc with temperature. But at least one site shows mean V-values which are clearly incompatible with this general trend.Finally, before proceeding further with studies of the distribution of V versus site parameters, we need to correct our V-measurements for the loss of gas which occurs when cutting the ice samples (and consequently opening air bubbles at the sample surface). We have developed, for this purpose, a technique which calculates random distributions of bubbles in the samples and counts the cut bubbles. This calculation depends on bubble shape and size as well as on sample volume and V. In the case of the samples used in the present study, between 3 and 10% of gas is typically lost during cutting. Bubble-size measurements have yet to be made before an accurate correction can be applied to the measurements presented here.
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Ng, W. F., W. M. Chakroun et M. Kurosaka. « Time‐resolved measurements of total temperature and pressure in the vortex street behind a cylinder ». Physics of Fluids A : Fluid Dynamics 2, no 6 (juin 1990) : 971–78. http://dx.doi.org/10.1063/1.857604.
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SUGIYAMA, SHIN, FRANCISCO J. NAVARRO, TAKANOBU SAWAGAKI, MASAHIRO MINOWA, TAKAHIRO SEGAWA, YUKIHIKO ONUMA, JAIME OTERO et EVGENY V. VASILENKO. « Subglacial water pressure and ice-speed variations at Johnsons Glacier, Livingston Island, Antarctic Peninsula ». Journal of Glaciology 65, no 252 (30 juillet 2019) : 689–99. http://dx.doi.org/10.1017/jog.2019.45.
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ABSTRACTTo study subglacial hydrological condition and its influence on the glacier dynamics, we drilled Johnsons Glacier on Livingston Island in the Antarctic Peninsula region. Subglacial water pressure was recorded in boreholes at two locations over 2 years, accompanied by high-frequency ice-speed measurements during two summer melt seasons. Water pressure showed two different regimes, namely high frequency and large amplitude variations during the melt season (January–April) and small fluctuations near the overburden pressure the rest of the year. Speed-up events were observed several times in each summer measurement period. Ice motion during these events substantially contributed to total glacier motion, for example, fast ice flow over 1 week accounted for ~70% of the total displacement over a 25-day long measurement period. We did not find a clear relationship between subglacial water pressure and ice speed. This was probably because subglacial hydraulic conditions were spatially inhomogeneous and thus our borehole data did not always represent a large-scale subglacial condition. Ice temperature measurements in the boreholes confirmed the existence of a cold ice layer near the glacier surface. Our data provide a basis to better understand the dynamic and hydrological conditions of relatively unstudied glaciers in the Antarctic Peninsula region.
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Hurst, D. F., E. G. Hall, A. F. Jordan, L. M. Miloshevich, D. N. Whiteman, T. Leblanc, D. Walsh, H. Vömel et S. J. Oltmans. « Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009 ». Atmospheric Measurement Techniques 4, no 12 (16 décembre 2011) : 2777–93. http://dx.doi.org/10.5194/amt-4-2777-2011.
Texte intégralRésumé :
Abstract. We compare coincident, in situ, balloon-borne measurements of temperature (T) and pressure (P) by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and similar measurements of relative humidity (RH) by RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with at least one pair of radiosondes are analyzed in 1-km altitude bins to quantify measurement differences between the sonde sensors and how they vary with altitude. Each comparison (T, P, RH) exposes several profiles of anomalously large measurement differences. Measurement difference statistics, calculated with and without the anomalous profiles, are compared to uncertainties quoted by the radiosonde manufacturers. Excluding seven anomalous profiles, T differences between 19 pairs of RS92 and iMet sondes exceed their measurement uncertainty limits (2 σ) 31% of the time and reveal a statistically significant, altitude-independent bias of 0.5 ± 0.2 °C. Similarly, RS92-iMet P differences in 22 non-anomalous profiles exceed their uncertainty limits 23% of the time, with a disproportionate 83% of the excessive P differences at altitudes >16 km. The RS92-iMet pressure differences increase smoothly from −0.6 hPa near the surface to 0.8 hPa above 25 km. Temperature and P differences between all 14 pairs of RS92 sondes exceed manufacturer-quoted, reproducibility limits (σ) 28% and 11% of the time, respectively. About 95% of the excessive T differences are eliminated when 5 anomalous RS92-RS92 profiles are excluded. Only 5% of RH measurement differences between 14 pairs of RS92 sondes exceed the manufacturer's measurement reproducibility limit (σ). RH measurements by RS92 sondes are also compared to RH values calculated from frost point hygrometer measurements and coincident T measurements by the radiosondes. The influences of RS92-iMet Tand P differences on RH values and water vapor mixing ratios calculated from frost point hygrometer measurements are examined.
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Payne, S. J., et A. J. W. Moxon. « High-Frequency Effects in the Aspirating Probe ». Journal of Turbomachinery 129, no 4 (9 octobre 2006) : 842–51. http://dx.doi.org/10.1115/1.2720872.
Texte intégralRésumé :
The aspirating probe has recently been successfully used to measure entropy within a turbomachine; however, it was found that its sensitivity to total pressure and total temperature fluctuations was significantly altered at high frequencies. If the aspirating probe is to be used to measure unsteady flow fields accurately, these high-frequency effects must be better understood. The analysis of this behavior presented here shows that there are three effects that must be considered: the frequency response of the hot wires, the presence of Mach number fluctuations inside the probe, and the change in heat transfer from the hot wires at high frequencies. A theoretical analysis of the first effect has provided a correction factor that can be used for any hot wire, dependent solely on the baseline heat transfer ratio, the overheat ratio, and the time constant of the hot wires. The second and third effects have been examined numerically, since no theoretical solution is known to exist. The Mach number fluctuations are found to be well predicted by a simple one-dimensional solver and to show a variation of ±2.4% in Mach number at the hot-wire plane for the geometry and flow field considered here. The variation in heat transfer with frequency is found to be negligible at high overheat ratios, but significant at overheat ratios below ∼0.4. Coefficients that determine how the measured total pressure and total temperature depend on the actual total pressure, total temperature, and Mach number have been derived, and these show significant variation with the values of the two overheat ratios. Using synthetic data, based on previous experimental data, the effects on the probe measurement accuracy are analyzed. This shows that the amplitudes of total pressure and total temperature are reduced. At widely spaced overheat ratios, the amplitudes are reduced by similar amounts, but at smaller spacing the reductions become dissimilar, resulting in highly erroneous entropy∕R measurements. High-frequency effects thus have a significant effect on the performance of the aspirating probe and should be carefully considered when using it in a highly unsteady flow field.
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Guha, Abhijit. « A Simple Analytical Theory for Interpreting Measured Total Pressure in Multiphase Flows ». Journal of Fluids Engineering 120, no 2 (1 juin 1998) : 385–89. http://dx.doi.org/10.1115/1.2820659.
Texte intégralRésumé :
This paper presents a simple, analytical theory for determining total pressure in multiphase flows, a subject of theoretical interest as well as of practical importance. It is shown here that the nonequilibrium processes occurring in the vicinity of a measuring device have a significant influence on the magnitude of flow velocity inferred from Pitot measurements. The present theory predicts that, depending on the size of the particles or droplets, the total pressure varies monotonically between the two limiting values: the frozen total pressure (when there is no interphase mass, momentum, and energy transfer in the decelerating flow toward the stagnation point) and the equilibrium total pressure (when the dispersed phase, either liquid droplets, or solid particles, is always at inertial and thermodynamic equilibrium with the continuous vapour phase). The presented analytical theory is a relation between nondimensional total pressure and Stokes number, representing particle size or inertia, and specifies the total pressure under different nonequilibrium conditions. One simple equation applies to diverse multiphase mixtures, solid particle laden gas as well as vapour-droplet mixtures, and at a wide range of flow conditions, both subsonic and supersonic. The associated issue of interpreting total temperature, and the relation between measured total pressure and entropy production in multiphase flows have been discussed at length by Guha (1998).
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Zhu, Lian Jun, Yu Cai Dong, Jian Guang Yuan, Liang Hai Yi et Ge Hua Fan. « Prediction of the Total Sound Level of the Annular Combustor Noise of Aircraft Engine Based on SVR ». Applied Mechanics and Materials 687-691 (novembre 2014) : 33–36. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.33.
Texte intégralRésumé :
Because of the high temperature and high pressure environment inside the annular combustor of an aircraft engine, the direct measurement of the burner noise is very difficult. This paper set up the model of the total sound level and the effect factor SVR though analyzing the relationship between the total sound level and noise parameters of the combustion chamber the annular combustor an aircraft engine and the influence factors,, and it is better than multiple regression mode and the projection pursuit regression model, and predict the predicting samples so it is important for aero-engine design and reliability analysis.
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Rahma, Sarah Nadhila, Mahfiro Risky Safitri et Abdul Rohim Tualeka. « The Analysis of Differences in Body Temperature and Blood Pressure Before and After Exposure to Hot Work Climates ». Indonesian Journal Of Occupational Safety and Health 9, no 3 (15 novembre 2020) : 318. http://dx.doi.org/10.20473/ijosh.v9i3.2020.318-327.
Texte intégralRésumé :
Introduction: Working in a hot work environment has a negative impact on occupational health and safety. The impact on health due to work at temperatures above a comfortable temperature can affect body temperature and blood pressure of workers. The aim of this study was to analyze the differences in body temperature and blood pressure of workers before and after exposure to hot work climates at PT. Pertamina (Persero) Tanjung Wangi. Method: This research was an observational study with cross sectional approach. The population of this study was all workers at PT. Pertamina (Persero) Tanjung Wangi., with the total of 11 people. The sample in this study was obtained by total sampling method with a sample of 11 workers. The dependent variables in this study were body temperature, blood pressure, age, fluid intake, and nutritional status, while the independent variable was work climate. Results: Most of the grass lathe workers at PT. Pertamina (Persero) Tanjung Wangi has an age between 17-25 years, some of the grass lathe workers had a fluid intake with less categories with normal nutritional status. The measurement results showed that the average ISBB value was 28.8°C, this value still exceeded TLV. In addition, the results showed that there were differences in body temperature before and after work, from 36.04° C to 36.8° C. In addition there were differences in systolic and diastolic blood pressure before work which was 112.7 mm Hg 77.3 mm Hg, and the average after work was 121 mm Hg and 83.6 mm Hg. Conclusion: There is a difference between body temperature and blood pressure before and after exposure to hot work climates.Keywords: blood pressure, body temperature, hot work climate
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Suryavamshi, N., B. Lakshminarayana et J. Prato. « Aspirating Probe Measurements of the Unsteady Total Temperature Field Downstream of an Embedded Stator in a Multistage Axial Flow Compressor ». Journal of Turbomachinery 120, no 1 (1 janvier 1998) : 156–69. http://dx.doi.org/10.1115/1.2841377.
Texte intégralRésumé :
The results from the area traverse measurements of the unsteady total temperature using a high-response aspirating probe downstream of the second stator of a three-stage axial flow compressor are presented. The measurements were conducted at the peak efficiency operating point. The unsteady total temperature data are resolved into deterministic and unresolved components. Hub and casing regions have high levels of unsteadiness and consequently high levels of mixing. These regions have significant levels of shaft resolved and unresolved unsteadiness. Comparisons are made between the total temperature and the total pressure data to examine the rotor 2 wake characteristics and the temporal variation of the stator exit flow. Isentropic efficiency calculations at the midpitch location show that there is about a 4 percent change in the algebraically averaged efficiency across the blades of the second rotor and if all the rotor 2 blades were behaving as a “best” blade, the improvement in efficiency would be about 1.3 percent. An attempt is made to create a composite flow field picture by correlating the unsteady velocity data with temperature and pressure data.
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Barbieri, Lindsay, Stephan Kral, Sean Bailey, Amy Frazier, Jamey Jacob, Joachim Reuder, David Brus et al. « Intercomparison of Small Unmanned Aircraft System (sUAS) Measurements for Atmospheric Science during the LAPSE-RATE Campaign ». Sensors 19, no 9 (10 mai 2019) : 2179. http://dx.doi.org/10.3390/s19092179.
Texte intégralRésumé :
Small unmanned aircraft systems (sUAS) are rapidly transforming atmospheric research. With the advancement of the development and application of these systems, improving knowledge of best practices for accurate measurement is critical for achieving scientific goals. We present results from an intercomparison of atmospheric measurement data from the Lower Atmospheric Process Studies at Elevation—a Remotely piloted Aircraft Team Experiment (LAPSE-RATE) field campaign. We evaluate a total of 38 individual sUAS with 23 unique sensor and platform configurations using a meteorological tower for reference measurements. We assess precision, bias, and time response of sUAS measurements of temperature, humidity, pressure, wind speed, and wind direction. Most sUAS measurements show broad agreement with the reference, particularly temperature and wind speed, with mean value differences of 1.6 ± 2.6 ∘ C and 0.22 ± 0.59 m/s for all sUAS, respectively. sUAS platform and sensor configurations were found to contribute significantly to measurement accuracy. Sensor configurations, which included proper aspiration and radiation shielding of sensors, were found to provide the most accurate thermodynamic measurements (temperature and relative humidity), whereas sonic anemometers on multirotor platforms provided the most accurate wind measurements (horizontal speed and direction). We contribute both a characterization and assessment of sUAS for measuring atmospheric parameters, and identify important challenges and opportunities for improving scientific measurements with sUAS.
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Mei, Fan, Steven Spielman, Susanne Hering, Jian Wang, Mikhail S. Pekour, Gregory Lewis, Beat Schmid, Jason Tomlinson et Maynard Havlicek. « Simulation-aided characterization of a versatile water-based condensation particle counter for atmospheric airborne research ». Atmospheric Measurement Techniques 14, no 11 (23 novembre 2021) : 7329–40. http://dx.doi.org/10.5194/amt-14-7329-2021.
Texte intégralRésumé :
Abstract. Capturing the vertical profiles and horizontal variations of atmospheric aerosols often requires accurate airborne measurements. With the advantage of avoiding health and safety concerns related to the use of butanol or other chemicals, water-based condensation particle counters have emerged to provide measurements under various environments. However, airborne deployments are relatively rare due to the lack of instrument characterization under reduced pressure at flight altitudes. This study investigates the performance of a commercial “versatile” water-based condensation particle counter (vWCPC, model 3789, TSI, Shoreview, MN, USA) under various ambient pressure conditions (500–920 hPa) with a wide range of particle total number concentrations (1500–70 000 cm−3). The effect of conditioner temperature on vWCPC 3789 performance at low pressure is examined through numerical simulation and laboratory experiments. We show that the default instrument temperature setting of 30 ∘C for the conditioner is not suitable for airborne measurement and that the optimal conditioner temperature for low-pressure operation is 27∘. Under the optimal conditioner temperature (27∘), the 7 nm cut-off size is also maintained. Additionally, we show that insufficient droplet growth becomes more significant under the low-pressure operation. The counting efficiency of the vWCPC 3789 can vary up to 20 % for particles of different chemical compositions (e.g., ammonium sulfate and sucrose particles). However, such variation is independent of pressure.
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Ganbavale, G., C. Marcolli, U. K. Krieger, A. Zuend, G. Stratmann et T. Peter. « Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions ». Atmospheric Chemistry and Physics Discussions 14, no 9 (19 mai 2014) : 12673–726. http://dx.doi.org/10.5194/acpd-14-12673-2014.
Texte intégralRésumé :
Abstract. This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T<270 K and T<260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.
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Ganbavale, G., C. Marcolli, U. K. Krieger, A. Zuend, G. Stratmann et T. Peter. « Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions ». Atmospheric Chemistry and Physics 14, no 18 (19 septembre 2014) : 9993–10012. http://dx.doi.org/10.5194/acp-14-9993-2014.
Texte intégralRésumé :
Abstract. This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature-dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T < 270 K and T < 260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high-temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.
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Yang, Lubing, Chuan Li et Chuan Luo. « Thermal Strain Detection for Concrete Structure Cold Shrinkage under Stress Constraint with FBG ». Sensors 22, no 24 (9 décembre 2022) : 9660. http://dx.doi.org/10.3390/s22249660.
Texte intégralRésumé :
Additional strain increments occur in concrete subject to stress constraints during cold shrinkage, resulting in irregular deformation and reducing the concrete structure’s stability. When an annular concrete structure is subjected to radial pressure, two tensile stress concentration zones will appear at the intersection of the inner wall and the diameter along the pressure direction. When exposed to low temperatures, the total strain in the tensile stress concentration zones is caused by the combined effect of applied stress strain and thermal strain. Then, the thermal strain of the structure can be obtained from the difference between the total strain and the applied stress strain. Gradient cooling was performed after applying radial pressure to the annular concrete using a counterforce device. The applied stress strain and total strain of the tensile stress concentration zones are measured by fiber Bragg grating (FBG) strain sensors fixed along the stress direction. According to the measurement results, the thermal strains of the concrete structure under the stress constraint are extracted to analyze the influence of the tensile stress constraint on the thermal strain of the concrete structure. In the temperature range of −40∘C∼20∘C, the thermal strains of the structure under radial pressures of 1500 N, 2000 N, and 3000 N are extracted, respectively. The thermal expansion coefficients are calculated based on the thermal strain of the structure. The free thermal expansion coefficient of concrete structures fluctuates around 11×10−6/∘C. When the temperature is reduced to 10∘C, the difference between the thermal expansion coefficient under the stress constraint and the free thermal expansion coefficient is the largest. When the temperature is reduced to −20∘C, the thermal expansion coefficients under each stress condition are close to the same. The results show that the stress confinement significantly inhibits the cold shrinkage of the concrete structure, and the inhibitory effect is gradually weakened when the temperature decreases.
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Yasa, T., G. Paniagua et R. Dénos. « Application of Hot-Wire Anemometry in a Blow-Down Turbine Facility ». Journal of Engineering for Gas Turbines and Power 129, no 2 (1 février 2006) : 420–27. http://dx.doi.org/10.1115/1.2364191.
Texte intégralRésumé :
In order to test HP turbine stages under engine representative conditions on a heat transfer point of view, blow-down test rigs are often used. In these rigs the evolution of gas temperature, pressure, and density is similar to a step function. Hence, the use of hot-wires, which are sensitive to flow velocity, density, and temperature, is more difficult than in an incompressible flow at constant temperature. This investigation describes how the data reduction can be performed in such an environment in order to extract the velocity. The gas temperature is measured with a thermocouple and the gas density is derived from the measurement of the total pressure thanks to an iterative procedure. Once the velocity is derived, the turbulence can be computed. The effectiveness of the method is first demonstrated in a heated jet where both pressure and temperature are varied. Tests in the turbine facility are performed at turbine inlet temperatures of 480K. Thus, overheat ratios up to 1.9 had to be used, leading to a very high temperature of the tungsten platinum coated wire. The aging of the probe was very fast, causing a drift in the voltage output between the successive tests. A technique is proposed to minimize the aging effect. It consists in adapting the calibration based on the resistance of the wire measured before each test. Measurements were carried out at the turbine inlet and rotor outlet. At the turbine inlet, velocity radial profiles are obtained together with measurements of the turbulence intensity. The time-averaged data is compared with pneumatic probe measurements. At the rotor exit, the time-resolved periodic velocity fluctuations are analyzed using a phase-locked average technique.
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Chen, Zehua, Zulong Zhao et Daoyong Yang. « Quantification of Phase Behavior for Solvent/Heavy-Oil/Water Systems at High Pressures and Elevated Temperatures with Dynamic Volume Analysis ». SPE Journal 25, no 06 (30 juin 2020) : 2915–31. http://dx.doi.org/10.2118/201240-pa.
Texte intégralRésumé :
Summary Accurate quantification of phase behavior of solvent/heavy-oil/bitumen/water systems at high pressures and elevated temperatures is of high significance for the design of vapor extraction, cyclic solvent injection, expanding-solvent steam-assisted gravity drainage (ES-SAGD), and hot-solvent injection processes. The relevant experimental data and theoretical analyses are still insufficient for achieving a reliable model. This is especially true when the system temperatures approach or exceed the critical temperatures of the solvents used (i.e., when the solvent density is large enough). This study provides new experimental measurements of the phase behavior of propane (C3H8)/carbon dioxide (CO2)/heavy-oil/water systems at pressures up to 20 MPa and temperatures up to 432.3 K. More specifically, four feeds of C3H8/CO2/heavy-oil/water systems are used to conduct constant composition expansion (CCE) tests, during which the heights of the entire fluid system (i.e., total volume) and each phase are recorded at each pressure and temperature, respectively. Theoretically, a dynamic volume analysis (DVA) of the measured data is proposed for the first time to quantify each phase, provided that the assumption for vapor phase is valid and that the vapor and oleic phase densities can be accurately calculated. By tuning the binary interaction parameter (BIP) for solvent/heavy-oil pairs (denoted as BIPS−HO) to match the total volume, the height of the vapor/oleic (V/L) interface can be matched as well. By using the tuned BIPS−HO, the total volume and height of the V/L interface of C3H8/CO2/heavy-oil/water systems can be accurately predicted, no matter whether the solvent solubility in water is low (i.e., C3H8) or high (i.e., CO2). This DVA can be used to determine/evaluate the solvent solubility, saturation pressure/phase boundary, and phase volume/density accurately in a large temperature and pressure range. The newly proposed DVA method is also used to reproduce the experimental measurements collected from the literature, including phase-volume fractions, solvent solubility, and saturation pressure. In addition, the DVA method can serve as a tool to check whether the experimental measurements are reliable or not.
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Bujoreanu, Carmen, Eugen Golgoţiu, Sorinel Gicu Talif et Gheorghe Manolache. « Experimental Investigation on Functional Parameters of the Engines Exhaust Mufflers ». Applied Mechanics and Materials 822 (janvier 2016) : 224–29. http://dx.doi.org/10.4028/www.scientific.net/amm.822.224.
Texte intégralRésumé :
The paper presents the results obtained by investigating some functional parameters as the noise level, the pressure – drop and the temperatures of three different manufacturing solutions for mufflers. The results emphasize the corroboration between these parameters and contribute to the improvement of the muffler fabrication and design since it is a complex function that affects noise characteristics, emission and fuel efficiency of engine. It was designed a measurement chain for the noise level evaluation of the mufflers including a microphone Bruel&Kjaer type 4133, a Impulse Precision Sound Level Meter Bruel&Kjaer, type 2209, with standard filters and a multifunctional external data acquisition board type-NI DAQPad-6015 . We assessed the noise level, using two based LabVIEW virtual instruments, measuring total band power and the equivalent continuous sound pressure level. It was also created a measurement chain for the pressure – drop evaluation and temperature distribution on the external surface of the mufflers.
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Odziemczyk, Waldemar. « Analysis of Deformations of the Skylight Construction at the Main Hall of the Warsaw University of Technology ». Reports on Geodesy and Geoinformatics 97, no 1 (3 février 2015) : 35–46. http://dx.doi.org/10.2478/rgg-2014-0010.
Texte intégralRésumé :
AbstractThe paper presents technology and results of measurements of the steel construction of the skylight of the Main Hall of the Warsaw University of Technology. The new version of the automated measuring system has been used for measurements. This system is based on Leica TCRP1201+ total station and the TCcalc1200 software application, developed by the author, which operates on a laptop computer connected with the total station by the wire. Two test measurements were performed. Each of them consisted of cyclic measurement using the polar method, from one station; points located on the skylight construction, as well as control points located on concrete, bearing poles, were successively measured. Besides geometrical values (such as Hz, V angles and the slope distance D), the changes of temperature and atmospheric pressure, were also recorded. Processed results of measurements contained information concerning the behaviour of the skylight; asymmetry of horizontal displacements with respect to the X axis have been proved. Changes of parameters of the instrument telescope and changes of the instrument orientation were also stated; they were connected with changes of the temperature. The most important results of works have been presented in the form of diagrams.
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Pasachoff, J. M., M. A. Peñaloza-Murillo, A. L. Carter et M. T. Roman. « Terrestrial atmospheric responses on Svalbard to the 20 March 2015 Arctic total solar eclipse under extreme conditions ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 374, no 2077 (28 septembre 2016) : 20160188. http://dx.doi.org/10.1098/rsta.2016.0188.
Texte intégralRésumé :
This article reports on the near-surface atmospheric response at the High Arctic site of Svalbard, latitude 78° N, as a result of abrupt changes in solar insolation during the 20 March 2015 equinox total solar eclipse and notifies the atmospheric science community of the availability of a rare dataset. Svalbard was central in the path of totality, and had completely clear skies. Measurements of shaded air temperature and atmospheric pressure show only weak, if any, responses to the reduced insolation. A minimum in the air temperature at 1.5 m above the ground occurred starting 2 min following the end of totality, though this drop was only slightly beyond the observed variability for the midday period. Eclipse-produced variations in surface pressure, if present, were less than 0.3 hPa. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.
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Matrosov, Sergey Y., et David D. Turner. « Retrieving Mean Temperature of Atmospheric Liquid Water Layers Using Microwave Radiometer Measurements ». Journal of Atmospheric and Oceanic Technology 35, no 5 (mai 2018) : 1091–102. http://dx.doi.org/10.1175/jtech-d-17-0179.1.
Texte intégralRésumé :
AbstractA remote sensing method to retrieve the mean temperature of cloud liquid using ground-based microwave radiometer measurements is evaluated and tested by comparisons with direct cloud temperature information inferred from ceilometer cloud-base measurements and temperature profiles from radiosonde soundings. The method is based on the dependence of the ratio of cloud optical thicknesses at W-band (~90 GHz) and Ka-band (~30 GHz) frequencies on cloud liquid temperature. This ratio is obtained from total optical thicknesses inferred from radiometer measurements of brightness temperatures after accounting for the contributions from oxygen and water vapor. This accounting is done based on the radiometer-based retrievals of integrated water vapor amount and temperature and pressure measurements at the surface. The W–Ka-band ratio method is applied to the measurements from a three-channel (90, 31.4, and 23.8 GHz) microwave radiometer at the U.S. Department of Energy Atmospheric Radiation Measurement Mobile Facility at Oliktok Point, Alaska. The analyzed events span conditions from warm stratus clouds with temperatures above freezing to mixed-phase clouds with supercooled liquid water layers. Intercomparisons of radiometer-based cloud liquid temperature retrievals with estimates from collocated ceilometer and radiosonde measurements indicated on average a standard deviation of about 3.5°C between the two retrieval types in a wide range of cloud temperatures, from warm liquid clouds to mixed-phase clouds with supercooled liquid and liquid water paths greater than 50 g m−2. The three-channel microwave radiometer–based method has a broad applicability, since it requires neither the use of active sensors to locate the boundaries of liquid cloud layers nor information on the vertical profile of temperature.
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COELHO-SOUZA, SERGIO A., FÁBIO V. ARAÚJO, JULIANO C. CURY, HUGO E. JESUS, GILBERTO C. PEREIRA, JEAN R. D. GUIMARÃES, RAQUEL S. PEIXOTO, ALBERTO M. R. DÁVILA et ALEXANDRE S. ROSADO. « Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ) ». Anais da Academia Brasileira de Ciências 87, no 3 (15 septembre 2015) : 1737–50. http://dx.doi.org/10.1590/0001-3765201520140098.
Texte intégralRésumé :
ABSTRACTUpwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.
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Sully, J. P., et R. G. Campanella. « Lateral stress measurements in a glaciomarine silty clay ». Geological Society, London, Engineering Geology Special Publications 7, no 1 (1991) : 265–70. http://dx.doi.org/10.1144/gsl.eng.1991.007.01.25.
Texte intégralRésumé :
AbstractThe paper presents the procedure used for installation of spade-like total stress cells (TSC) in an overconsolidated silty clay and subsequent interpretation of the data obtained. Prior to installation, all the spade cells were calibrated in the laboratory for both pressure and temperature effects. After extraction from the ground, the stress cells were recalibrated and changes in the calibration characteristics were noted. These changes presumably result from the effects of installation. The stress cells were read over a period of three months. The measured stresses, pore pressures and temperatures are evaluated to provide a profile of the lateral stress coefficient for the site.
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de Boer, Gijs, Darielle Dexheimer, Fan Mei, John Hubbe, Casey Longbottom, Peter J. Carroll, Monty Apple et al. « Atmospheric observations made at Oliktok Point, Alaska, as part of the Profiling at Oliktok Point to Enhance YOPP Experiments (POPEYE) campaign ». Earth System Science Data 11, no 3 (30 août 2019) : 1349–62. http://dx.doi.org/10.5194/essd-11-1349-2019.
Texte intégralRésumé :
Abstract. Between 1 July and 30 September 2018, small unmanned aircraft systems (sUAS), tethered balloon systems (TBSs), and additional radiosondes were deployed at Oliktok Point, Alaska, to measure the atmosphere in support of the second special observing period for the Year of Polar Prediction (YOPP). These measurements, collected as part of the Profiling at Oliktok Point to Enhance YOPP Experiments (POPEYE) campaign, targeted quantities related to enhancing our understanding of boundary layer structure, cloud and aerosol properties and surface–atmosphere exchange and providing extra information for model evaluation and improvement work. Over the 3-month campaign, a total of 59 DataHawk2 sUAS flights, 52 TBS flights, and 238 radiosonde launches were completed as part of POPEYE. The data from these coordinated activities provide a comprehensive three-dimensional data set of the atmospheric state (air temperature, humidity, pressure, and wind), surface skin temperature, aerosol properties, and cloud microphysical information over Oliktok Point. These data sets have been checked for quality and submitted to the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program data archive (http://www.archive.arm.gov/discovery/, last access: July 2019) and are accessible at no cost by all registered users. The primary dataset DOIs are https://doi.org/10.5439/1418259 (DataHawk2 measurements; Atmospheric Radiation Measurement Program, 2016), https://doi.org/10.5439/1426242 (TBS measurements; Atmospheric Radiation Measurement Program, 2017) and https://doi.org/10.5439/1021460 (radiosonde measurements; Atmospheric Radiation Measurement Program, 2013a).
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Pereira, Flávia Helena, Marcelo Eduardo Batalhão et Evelin Capellari Cárnio. « Correlation between body temperature, blood pressure and plasmatic nitric oxide in septic patients ». Revista Latino-Americana de Enfermagem 22, no 1 (janvier 2014) : 123–28. http://dx.doi.org/10.1590/0104-1169.2896.2392.
Texte intégralRésumé :
OBJECTIVE: to investigate whether there is a relationship between plasmatic levels of nitrate, body temperature, and blood pressure values in patients with sepsis, severe sepsis and septic shock. METHOD: prospective observational study performed in a Brazilian hospital; data were collected from July to December 2009. Thirty blood samples were obtained from a total of 29 patients. Blood samples (10ml) were collected for subsequent laboratory analysis to determine nitrate levels in the plasma. RESULTS: nitric oxide synthesis is increased in patients with septic shock, and is inversely correlated to the body temperature values. CONCLUSION: these data show that the measurement of body temperature and the observation of hypothermic conditions in septic patients could be important to guide the nursing regarding the evolution of individuals with sepsis to septic shock.
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Dang, Son, Carl Sondergeld et Chandra Rai. « Effects of gas pressurization on the interpretation of NMR hydrocarbon measurements in organic rich shales ». E3S Web of Conferences 146 (2020) : 03008. http://dx.doi.org/10.1051/e3sconf/202014603008.
Texte intégralRésumé :
The estimation of total hydrocarbons (HCs) in place is one of the most important economic challenges in unconventional resource plays. Nuclear magnetic resonance (NMR) has proven to be a valuable tool in directly quantifying both hydrocarbons and brines in the laboratory and the field. Some major applications of NMR interpretation include pore body size distributions, wettability, fluid types, and fluid properties. However, for tight formations, the effects of the factors on NMR relaxation data are intertwined. One purpose of this study is to review the interpretation of NMR response of HCs in a tight rock matrix through illustrated examples. When comparing NMR data between downhole wireline and laboratory measurement, three important elements need to be considered: 1) temperature differences, 2) system response differences, and 3) pressure (mainly due to the lost gasses.) The effect of temperature on HCs would be presented with experimental results for bulk fluids. Whereas, the effect of pressure is investigated by injecting gas back into rock matrix saturated with original fluids. The experiments were performed within an NMR transparent Daedalus ZrO2 pressure cell, which operates at pressures up to 10,000 psi. The results show that, at ambient temperature and pressure, NMR responds to a fraction of HCs, which is volatile enough to be observed as an NMR relaxation sequence. The invisible fraction of HCs to NMR sequence at ambient condition can be up to 20% of the total extractable HCs. Molecular relaxation is impacted by fluid viscosity, pore size, and surface affinity. In other words, the fluid with higher viscosity (either due to temperature or gas loss), presenting in smaller pore, or highly affected by the pore surface, will relax faster, and would be partially invisible to NMR, especially in the field. This is critical to the interpretation of NMR response for liquid rich source rocks, in which all of the above molecular relaxing restrictions can be found. Thus, engineers can underestimate movable HCs by using routine core analysis data.
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Haji, M., et L. C. Chow. « Experimental Measurement of Water Evaporation Rates Into Air and Superheated Steam ». Journal of Heat Transfer 110, no 1 (1 février 1988) : 237–42. http://dx.doi.org/10.1115/1.3250457.
Texte intégralRésumé :
The rates of evaporation of water from a horizontal water surface into a turbulent stream of hot air or superheated steam at different free-stream mass fluxes and modulated temperatures were experimentally measured. The pressure of the free stream was atmospheric. For steam, the experimental results are mostly within 10 percent of the available analytical results. Two previous experimental results are about 50 percent and 300 percent higher than the analytical results. For air, the measured evaporation rates are consistently higher than the analytical results. An estimate of the conduction heat transfer from the walls of the test section to water was made for several air tests. If the conduction heat transfer were subtracted from the total heat transfer, the measured evaporation rates are actually quite close to the analytical results. The present experiment also confirms the existence of a temperature, called the inversion temperature, below which the water evaporation rate is higher in air than in steam, but above which the opposite is true. The inversion temperature is in good agreement with the analytical prediction. The results for both air and superheated steam show that a certain scaled expression for the evaporation rate is independent of the free-steam mass flux, also in agreement with the analytical prediction.
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Needham, D., et R. M. Hochmuth. « Rapid Flow of Passive Neutrophils Into a 4 μm Pipet and Measurement of Cytoplasmic Viscosity ». Journal of Biomechanical Engineering 112, no 3 (1 août 1990) : 269–76. http://dx.doi.org/10.1115/1.2891184.
Texte intégralRésumé :
Neutrophils from five different individuals are isolated with a density separation technique. A total of 151 unactivated (passive) cells are rapidly aspirated at constant suction pressure and at room temperature into a pipet with a diameter of 4 μm. The suction pressures in excess of an initial yield threshold are 0.5, 1 and 2 kPa and are comparable to those encountered in the microcirculation. These pressures are well in excess of the small suction pressure of ~ 20 Pa that is required to form a static hemispherical bump on the cell. At a given aspiration pressure, the leading edge of an individual cell is “tracked” as it flows into the pipet. A theory based on the flow of a Newtonian liquid from either a hemisphere or a spherical segment into a cylinder is used to model the entry process. Both theory and experiment show that during most of the entry process the leading edge of the cell moves at a nearly constant velocity with a rapid acceleration at the end. For cells from five different individuals at the three different excess aspiration pressures, Newtonian theory gives a cytoplasmic viscosity of 135 ± 54 Pa·s and overall entry times of 3.3s (0.5 kPa), 1.6s (1 kPa) and 0.82s (2 kPa). These results and those of Evans and Yeung at lower aspiration pressures indicate that the complex cytoplasm inside unactivated neutrophils behaves as a nearly Newtonian fluid with a viscosity on the order of 102 Pa·s over almost a two order of magnitude range in aspiration pressure and, thus, rate of deformation.
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Fang, Jing, et I.-Ming Chou. « Redox control and measurement in low-temperature (<450 °C) hydrothermal experiments ». American Mineralogist 106, no 8 (1 août 2021) : 1333–40. http://dx.doi.org/10.2138/am-2021-7687.
Texte intégralRésumé :
Abstract Redox control in hydrothermal experiments is routinely achieved through double-capsule and Shaw membrane techniques. These techniques control oxygen fugacity (fO2) by imposing a defined hydrogen fugacity (fH2) on a studied sample enclosed, together with H2O, in a hydrogen membrane capsule made of Pt or Ag-Pd alloys. However, due to the low permeability of these membranes to H2 at low temperatures (T), these techniques do not work efficiently below 450 °C. Here, we tested fused silica as a new hydrogen membrane and successfully applied it to monitor and control the redox states of studied samples at T down to 200 °C in hydrothermal experiments. Our results showed that 3, 8, 16, 36, 96, and 216 h are sufficient for a fused silica capillary capsule (FSCC) to reach osmotic equilibrium with the externally imposed 1 bar of H2 at 350, 300, 250, 200, 150, and 100 °C, respectively, and H2 pressures inside a FSCC was very close to the externally imposed values after osmotic equilibrium. By using FSCC as a hydrogen fugacity sensor, equilibrium H2 pressures for Ni-NiO-H2O and Co-CoO-H2O redox buffer assemblages at 250–400 °C and 1000 bar total pressure were measured. The equilibrated fO2 calculated are consistent with those derived from previous literature. Besides, FSCC can be used as a sample container, where fH2 and fO2 of enclosed samples can be continuously controlled. Furthermore, FSCC is an ideal container for sulfur-bearing samples, and its transparency allows spectroscopic analyses of the sample. Our work extended the low-T limit of previously well-developed redox control techniques and may open up a new research avenue in low-T hydrothermal experiments.
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Gossweiler, C. R., P. Kupferschmied et G. Gyarmathy. « On Fast-Response Probes : Part 1—Technology, Calibration, and Application to Turbomachinery ». Journal of Turbomachinery 117, no 4 (1 octobre 1995) : 611–17. http://dx.doi.org/10.1115/1.2836579.
Texte intégralRésumé :
A system for fast-response probe measurements in turbomachine flows has been developed and tested. The system has been designed for 40 kHz bandwidth and used with various in-house built probes accommodating up to four piezoresistive pressure transducers. The present generation of probes works accurately up to several bar pressure and 120°C temperature. The probes were found to be quite robust. The use of a miniature pressure transducer placed in the head of a probe showed that a precise packaging technique and a careful compensation of errors can considerably improve the accuracy of the pressure measurement. Methods for aerodynamic probe calibration and off-line data evaluation are briefly presented. These aimed, e.g., in the case of a four-hole probe, at measuring the velocity fluctuations as characterized by yaw, pitch, total pressure, and static pressure and at deriving mean values and spectral or turbulence parameters. Applications of the measuring system to turbomachinery flow in a radial compressor and to a turbulent pipe flow demonstrate the performance of the measuring system.
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Haris, Dendi, et Dian Sutono Hs. « Performance Study Of 1.3 Ton Slurry Ice Machine Capacity In Cold Chain Fish Handling ». Barakuda 45 : Jurnal Ilmu Perikanan dan Kelautan 4, no 2 (11 novembre 2022) : 168–79. http://dx.doi.org/10.47685/barakuda45.v4i2.273.
Texte intégralRésumé :
Slurry ice is a solution to improve the quality of fish caught and cultured. The purpose of this research is to analyze and test the performance of the slurry ice machine. The analysis used includes calculating the power performance coefficient (COP), refrigeration capacity (Q), refrigerant flow rate, volume flow rate, compressor work (WComp). The heat released by the condenser and the heat absorbed by the refrigerant in the evaporator. The calculation uses data from the measurement of condenser temperature, compressor pressure. Methods to calculate the calculation of specification data and pressure from the compressor use formulas. The results showed that COP = 3.8-4.3, Qtot = 9-10 kW (for each hour), m = 0.06 kg/s, Wcomp = 2.35-2, 6 kW, Qcond = 12, 4-12.52 kW, Qevap = 9.8-10.17 kW, the total refrigeration load for 24 hours is 228 kW. The total production of slurry ice for 24 hours is 1,396.8 kg or 1.3968 Tons. The results of the test on catfish that were cooled using slurry ice, the decrease in temperature from the initial temperature of catfish 27.8°C to a temperature of (-0.7°C) took 36 minutes. Meanwhile, chilled catfish using shaved ice with an initial temperature of 27.8°C catfish to 2°C takes 1 hour.
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Gui, Tai Long, Si Da Jiang, Chun Cheng Ban et Jia Qing Liu. « Preparation and Character Measurements of AlN Films for RF Magnetron Sputtering ». Advanced Materials Research 663 (février 2013) : 409–12. http://dx.doi.org/10.4028/www.scientific.net/amr.663.409.
Texte intégralRésumé :
AlN dielectric thin films were deposited on N type Si(100) substrate by reactive radio frequency magnetron sputtering that directly bombardment AlN target under different sputtering-power and total pressure. The crystal structure,composition,surface and refractive index of the thin films were studied by XRD, SEM, AFM and elliptical polarization instrument. The results show that the surface and refractive of the thin films strongly depends on the sputtering-power and total pressure,the good uniformity and smoothness is found at 230 W, Ar flow ratio 5.0 LAr/sccm, substrate temperature 100°Cand 1.2 Pa. The crystal structure of the as-deposited thin-films is amorphous，then it transforms from blende structure to wurtzite structure as the rapid thermal annealing(RTA) temperature changes from 600 to 1200°C. The refractive index also increases with the RTA temperature it is increasing significantly from 800 to 1000°C．
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Tarigan, Sumiati, Saldy Yusuf et Yuliana Syam. « Effect of interface pressure and skin surface temperature on pressure injury incidence : a turning schedule pilot study ». Journal of Wound Care 30, no 8 (2 août 2021) : 632–41. http://dx.doi.org/10.12968/jowc.2021.30.8.632.
Texte intégralRésumé :
Objective: This study aimed to evaluate the interface pressure and skin surface temperature in relation to the incidence of pressure injury (PI) using three different turning schedules. Method: This was a pilot study with a three-armed randomised clinical trial design. Participants at risk of PI and treated in the high dependency care unit in a regional hospital in Makassar, Indonesia participated in this study. Patients were repositioned at three different turning schedules (two-, three- and four-hourly intervals). Interface pressure measurement and skin surface temperature were measured between 14:00 and 18:00 every three days. The incidence of PI was assessed during the two-week observation period. Results: A total of 44 participants took part in the study. A one-way ANOVA test revealed no difference in interface pressure among the three different turning schedule groups within two weeks of observations: day zero, p=0.56; day four, p=0.95; day seven, p=0.56; day 10, p=0.63; and day 14, p=0.92. Although the average periumbilical temperature and skin surface temperature were not significant (p>0.05), comparison between these observation sites was significant on all observation days (p<0.05). Regarding the incidence of PI, the proportional hazard test for the development of PI in the three groups was considered not different (hazard ratio: 1.46, 95% confidence interval: 0.43–4.87, p=0.54). Conclusion: No difference in interface pressure and incidence of PI on the three turning schedules was observed; however, there was a potential increase in skin surface temperature in comparison with periumbilical temperature for all three turning schedules.
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Purgar, Marija, Damir Kapetanović, Ana Gavrilović, Branimir K. Hackenberger, Božidar Kurtović, Ines Haberle, Jadranka Pečar Ilić et al. « Dataset AqADAPT : Physicochemical Parameters, Vibrio Abundance, and Species Determination in Water Columns of Two Adriatic Sea Aquaculture Sites ». Data 8, no 3 (3 mars 2023) : 55. http://dx.doi.org/10.3390/data8030055.
Texte intégralRésumé :
Aquaculture provides more than 50% of all seafood for human consumption. This important industrial sector is already under pressure from climate-change-induced shifts in water column temperature, nutrient loads, precipitation patterns, microbial community composition, and ocean acidification, all affecting fish welfare. Disease-related risks are also shifting with important implications for risk from vibriosis, a disease that can lead to massive economic losses. Adaptation to these pressures pose numerous challenges for aquaculture producers, policy makers, and researchers. The dataset AqADAPT aims to help the development of management and adaptation tools by providing (i) measurements of physicochemical (temperature, salinity, total dissolved solids, pH, dissolved oxygen, conductivity, transparency, total nitrogen, ammonia, nitrate, nitrite, total phosphorus, total particulate matter, particulate organic matter, and particulate inorganic matter) and microbiological (heterotrophic (total) bacteria, fecal indicators, and Vibrio abundance) parameters of seawater and (ii) biochemical determination of culturable bacteria in two locations near floating cage fish farms in the Adriatic Sea. Water sampling was conducted seasonally in two fish farms (Cres and Vrgada) and corresponding reference (control) sites between 2019 and 2021 of four vertical layers for a total of 108 observations: the surface, 6 m, 12 m, and the bottom.
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Frankenberg, C., U. Platt et T. Wagner. « Iterative maximum a posteriori (IMAP)-DOAS for retrieval of strongly absorbing trace gases : Model studies for CH<sub>4</sub> ; and CO<sub>2</sub> ; retrieval from near infrared spectra of SCIAMACHY onboard ENVISAT ». Atmospheric Chemistry and Physics Discussions 4, no 5 (29 septembre 2004) : 6067–106. http://dx.doi.org/10.5194/acpd-4-6067-2004.
Texte intégralRésumé :
Abstract. In the past, differential optical absorption spectroscopy (DOAS) has mostly been employed for trace gas retrieval in the UV/Vis spectral region. New spectrometers such as SCIAMACHY onboard ENVISAT also provide near infrared channels and thus allow for the detection of greenhouse gases like CH4, CO2, or N2O. However, modifications of the classical DOAS algorithm are necessary to account for the idiosyncrasies of this spectral region, i.e. the temperature and pressure dependence of the high resolution absorption lines. Furthermore, understanding the sensitivity of the measurement of these high resolution, strong absorption lines by means of a non-ideal device, i.e. having finite spectral resolution, is of special importance. This applies not only in the NIR, but can also prove to be an issue for the UV/Vis spectral region. This paper presents a modified iterative maximum a posteriori-DOAS (IMAP-DOAS) algorithm based on optimal estimation theory introduced to the remote sensing community by Rodgers (1976). This method directly iterates the vertical column densities of the absorbers of interest until the expected total optical density fits the measurement. Although the discussion in this paper lays emphasis on satellite retrieval, the basic principles of the algorithm also hold for arbitrary measurement geometries. For a quantitative test of this new approach and a comparison with classical algorithms, it is applied to modelled spectra based on a comprehensive set of atmospheric temperature and pressure profiles. This analysis reveals that the sensitivity of measurement strongly depends on the prevailing pressure-height. The IMAP-DOAS algorithm properly accounts for the sensitivity of measurement on pressure due to pressure broadening of the absorption lines. Thus, biases in the retrieved vertical columns that would arise in classical algorithms, are obviated. Here, we analyse and quantify these systematic biases as well as errors due to variations in the temperature and pressure profiles, which is indispensable for the understanding of measurement precision and accuracy in the near infrared as well as for future intercomparisons of retrieval algorithms.