Littérature scientifique sur le sujet « Measurement burst design »
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Articles de revues sur le sujet "Measurement burst design"
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Rast, Philippe, Stuart W. S. MacDonald et Scott M. Hofer. « Intensive Measurement Designs for Research on Aging ». GeroPsych 25, no 2 (janvier 2012) : 45–55. http://dx.doi.org/10.1024/1662-9647/a000054.
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Intensive measurement burst designs permit analysis of behavioral and biological processes as they unfold over short and long periods of time and providing the opportunity to identify change from an individual’s normative level of functioning. The measurement burst design permits statistical decomposition of short-term variation and learning effects that overlay normative aging and provide stronger bases for detecting accelerated change due to pathological processes. We provide an overview of design features and analysis of measurement burst data in Project MIND. The objective of intensive measurement designs is to obtain greater resolution of processes of interest that permit reliable and sensitive assessments of functioning and change in functioning and of key determinants underlying short-term variation and long-term aging and health-related change.
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Oravecz, Zita, Nelson Roque et Martin Sliwinski. « Bayesian Modeling of Cognitive Impairment in the Presence of Retest Effects ». Innovation in Aging 4, Supplement_1 (1 décembre 2020) : 566. http://dx.doi.org/10.1093/geroni/igaa057.1870.
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Abstract Diagnosing the early onset of neuropathologies, such as mild cognitive impairment (MCI), requires repeated evaluation of cognitive skills several times per year -- a measurement design known as a “burst design.” Detecting the often subtle cognitive decline in the presence of retest effects requires careful statistical modeling. The double exponential model offers a modeling framework to account for retest gains across measurement bursts, as well as warm-up effects within a burst, while quantifying change across bursts in peak performance. This talk highlights how a Bayesian multilevel implementation of the double exponential model allows for flexible extensions of this framework in terms of accommodating different timescales (nesting) and person-level predictors and drawing intuitive inferences on cognitive change with Bayesian posterior probabilities. We will use reaction time data to show how individual differences in asymptotic performance and change can be related to predictors such as age and MCI status. Part of a symposium sponsored by the Measurement, Statistics, and Research Design Interest Group.
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Alessandri, Guido, Evelina De Longis et Gianluca Cepale. « Emotional inertia emerges after prolonged states of exhaustion : Evidences from a measurement burst study ». Motivation and Emotion 45, no 4 (20 avril 2021) : 518–29. http://dx.doi.org/10.1007/s11031-021-09884-4.
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AbstractExhaustion refers to the feeling of ongoing loss of emotional, physical and cognitive resources. The present study draws on the Conservation of Resources Theory to examine the relationship between chronic exhaustion and negative emotional inertia among 206 employees (aged between 19 and 50 years; M = 21.03; SD = 2.98), in a naturalistic setting. To this purpose, we used a measurement burst design with two intensive bursts—spaced 1 month apart—by repeatedly sampling exhaustion and negative affect with 18 daily diaries (a morning and an evening assessment each day) per burst. After controlling for potential confounders, results showed that exhaustion at Burst 1 predicted negative emotional inertia at Burst 2, and not the other way around. These findings advance the knowledge on the relationship between exhaustion and negative emotional inertia by providing further insights on the likely direction of causality between study variables, that is from exhaustion to inertia (but not vice versa). Practical implication, limitations, and directions for future research are also discussed.
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Harrington, Karra, Nelson Roque et Jacqueline Mogle. « Approaches for Modeling of Intensive Longitudinal Data to Understand Cognitive Aging ». Innovation in Aging 4, Supplement_1 (1 décembre 2020) : 565. http://dx.doi.org/10.1093/geroni/igaa057.1867.
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Abstract Understanding age-related change in cognition and identification of pathological changes requires sensitive and valid measurement of cognitive performance across time. Technological advances, such as ambulatory assessment of cognition using smartphones, have enabled intensive longitudinal methods where data is collected with many measurements over time. Our research group has developed novel ambulatory assessments that provide reliable, sensitive, and ecologically valid measurement of cognition across multiple timescales; from momentary changes to change across years. This symposium will present a spectrum of approaches to analysis of intensive longitudinal data that can inform models of cognitive aging. All three presentations will draw on data from measurement burst studies that apply our ambulatory cognitive assessment methods in community-based samples (i.e., systematically recruited in the Bronx, New York). For each measurement burst, participants undergo assessment consisting of brief surveys and cognitive tests via smartphone, up to 7 times per day across 14 days. Oravecz et al. will discuss the application of a Bayesian multilevel implementation of the double exponential model to account for retest effects while quantifying change in peak cognitive performance across time. Kang et al., will demonstrate a growth curve modeling approach for assessing the effects of between-person variables (i.e., loneliness) on change in cognition across measurement bursts. Harrington et al., will demonstrate a model-based cluster analysis approach, leveraging ambulatory assessments of subjective and objective cognitive function to unpack latent groups as a function of age and loneliness. Measurement, Statistics, and Research Design Interest Group Sponsored Symposium.
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Kang, Jee-eun, Karra Harrington et Martin Sliwinski. « Loneliness and Cognitive Functioning Over Time : Using Ambulatory Cognitive Assessment ». Innovation in Aging 4, Supplement_1 (1 décembre 2020) : 566. http://dx.doi.org/10.1093/geroni/igaa057.1869.
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Abstract Loneliness has been investigated as a risk factor for cognitive health, but results were inconsistent. This study used three measurement bursts of ambulatory cognitive assessment to determine whether loneliness affects longitudinal changes in cognitive functioning in daily life. At each burst, participants performed cognitive assessment five times a day for 14 days. 138 adults (Mage=49.4) who completed all three bursts were included in this study. Growth curve modeling showed that, on average, scores of cognitive functioning were improved across a 2 year period (p<.001). The chronic lonely group (in the highest tertile at all 3 bursts) showed less improvement in scores compared to non-lonely people (p<.01), although there was no difference in cognitive functioning at the baseline between two groups. This study indicates that we need a repeated measurement of cognitive functioning and longitudinal approach to detect the effect of chronic loneliness on the rate of cognitive change. Part of a symposium sponsored by the Measurement, Statistics, and Research Design Interest Group.
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Chang, Yaw-Jen, Shia-Chung Chen et Cheng-Li Hsu. « Study on Microchannel Design and Burst Frequency Detection for Centrifugal Microfluidic System ». Advances in Materials Science and Engineering 2013 (2013) : 1–9. http://dx.doi.org/10.1155/2013/137347.
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A centrifugal microfluidic system has been developed in this study, enabling the control and measurement of the burst frequency in order to manipulate the liquid. The radial microfluid chips with different microchannel dimensions were designed for simulation analyses and experimental verifications. The microfluidic flow in the microchannel was analyzed using software CFDRC, providing an accurate result compared with that from experiment. The results show that the design of the overflow microchannel can correctly keep the liquid volume with error as low as 5%. For mercurochrome, the burst frequency has an inverse proportion to the channel width, and the simulation results agree with the experimental results. For oil, however, the experimental and simulation results indicate that the relationship between the burst frequency and channel width is not obvious due to oil properties. Since the simulation approach can provide an accurate prediction of flow behavior in the microchannel, the design of radial microfluid chip and the control of burst frequency can be achieved effectively. A practical application to design the centrifugal microfluidic disc for blood typing test was also carried out in this study. The centrifugal microfluidic system can successfully control the spinning speed to achieve the result of adding reagents in a specific sequence.
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Zha, Bing Ting, He Zhang et Xiang Jin Zhang. « System for Measuring the Burst Point Time Base on APD ». Advanced Materials Research 860-863 (décembre 2013) : 2838–41. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.2838.
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Aiming at the burst point time measuring device cannot timely show the burst point time measurement situation, a new measuring system was designed. The pulse signal when the ammo was outing of the muzzle and exploding was detected by APD, the light pulse was converted to voltage pulse through an amplifying circuit. The timing display module was designed, the timing circuit got the voltage pulse and timing, and then the burst point time would show on LCD. All the photoelectric detector module was fixed with the special mechanical properties. The system could increase the maximum detection distance effectively, improve its detecting precision, and display the burst point time immediately. With the simulation experiment, the system had no failing to get the burst point time, and owned a stable performance. This design can provide a reference for the optimization and improvement of the burst point time measuring device.
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Holtzer, Roee, Frederick Foley, Vanessa D’Orio, Jessica Spat, Melissa Shuman et Cuiling Wang. « Learning and cognitive fatigue trajectories in multiple sclerosis defined using a burst measurement design ». Multiple Sclerosis Journal 19, no 11 (25 février 2013) : 1518–25. http://dx.doi.org/10.1177/1352458513477922.
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Background: Compromised learning and cognitive fatigue are critical clinical features in multiple sclerosis. Objectives: This study was designed to determine the effect of repeated exposures within and across study visits on performance measures of learning and cognitive fatigue in relapsing–remitting multiple sclerosis (RRMS). Methods: Thirty patients with RRMS and 30 controls were recruited. Using a burst measurement design (i.e. repeated assessments within and across study visits) the oral version of the Symbol Digit Modalities Test (SDMT) was administered three times during the baseline and two consecutive monthly follow-up visits for a total of nine test administrations. Learning was assessed within and across study visits whereas cognitive fatigue was assessed during the course of each test administration that was divided into three 30-second intervals. Results: Linear mixed-effect models revealed compromised learning within (95% CI: 2.6355 to 3.9867) and across (95% CI: 1.3250 to 3.1861) visits and worse cognitive fatigue (95% CI: −2.1761 to −0.1720) in patients with RRMS compared with controls. Among patients with RRMS, worse self-rated cognitive dysfunction predicted poor learning within (95% CI: −0.1112 to −0.0020) and across (95% CI: −0.0724 to −0.0106) visits. Conclusions: Burst design is optimal to study learning and cognitive fatigue. This methodology, using the SDMT or other time-efficient tests as outcome measures, can be successfully implemented in longitudinal studies and clinical trials.
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Patrick, Megan E., Jennifer L. Maggs et Eva S. Lefkowitz. « Daily Associations Between Drinking and Sex Among College Students : A Longitudinal Measurement Burst Design ». Journal of Research on Adolescence 25, no 2 (4 avril 2014) : 377–86. http://dx.doi.org/10.1111/jora.12135.
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Griffin, Jamie, et Megan E. Patrick. « Understanding Participation in a Web-Based Measurement Burst Design : Response Metrics and Predictors of Participation ». Survey Practice 8, no 3 (1 juin 2015) : 1–11. http://dx.doi.org/10.29115/sp-2015-0011.
Texte intégralThèses sur le sujet "Measurement burst design"
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Prieskorn, Zachary Ryan. « Design and testing of a NITPC X-ray polarimeter with applications for the measurement of SGR burst polarization ». Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1061.
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Soft gamma repeaters (SGRs) are neutron stars with ultra-strong magnetic fields, on the order of 1014 G. As the source of the strongest magnetic fields in the universe, they are ideal objects to study the behavior of matter and light in this extreme environment. SGRs emit recurrent short duration, 0.1s, bursts of soft gamma-rays/hard X-rays that are expected to be highly polarized in the 2-10 keV energy range. By measuring the polarization of these bursts we can learn about the strength and configuration of the magnetic fields, the geometry of the emission region and the mass/radius relationship of the neutron star. Using the archival RXTE/PCA data we analyzed ~3 Ms of observations for SGR1806-20 and SGR1900+14. Over 5000 bursts were detected from the sources and each distribution of burst fluence was found to be well fit by a power law with an exponent of 1.60±0.02 for SGR1806-20 and 1.64±0.03 for SGR1900+14. The power law form holds over 4 magnitudes of fluence and the exponents were found to be independent of the level of burst activity. The exponent values suggest that SGR bursts are associated with a self-organized critical system, similar to earthquakes.
To measure the polarization of SGR bursts a wide-field-of-view, large area detector is needed. To accomplish this we designed and tested a negative ion time projection chamber (NITPC) X-ray polarimeter which uses nitromethane (CH3NO¬2) as an electronegative gas additive. Utilizing a double gas electron multiplier (GEM) NITPC with CO2+CH3NO2 as a gas mixture we successfully measured gas gains, imaged photoelectron tracks and measured distributions of their length, measured drift velocity of negative ions in various electric fields, and measured modulation from polarized and unpolarized X-ray sources between 3 and 8 keV. Based on the lab instrument results and our SGR burst fluence analysis we propose an instrument appropriately sized for a NASA Small Mission Explorer Mission (SMEX) that would be capable of measuring the polarization of hundreds of bursts from an SGR in a state of high burst activity.
Livres sur le sujet "Measurement burst design"
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Bukowski, William M., Ryan J. Persram, Bianca Panarello, Melisa Castellanos et Lisa Astrologo. Measurement Burst Designs to Improve Precision in Peer Research. University of Cambridge ESOL Examinations, 2021.
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Bukowski, William M., Ryan J. Persram, Bianca Panarello, Melisa Castellanos et Lisa Astrologo. Measurement Burst Designs to Improve Precision in Peer Research. University of Cambridge ESOL Examinations, 2021.
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Bukowski, William M., Ryan J. Persram, Bianca Panarello, Melisa Castellanos et Lisa Astrologo. Measurement Burst Designs to Improve Precision in Peer Research. University of Cambridge ESOL Examinations, 2021.
Trouver le texte intégralChapitres de livres sur le sujet "Measurement burst design"
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Magee, Patrick, et Mark Tooley. « Monitoring Depth of Anaesthesia ». Dans The Physics, Clinical Measurement and Equipment of Anaesthetic Practice for the FRCA. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199595150.003.0023.
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There are, and have been, many monitors designed to monitor depth of anaesthesia and to give an indication of awareness during surgery, which use electrical signals obtained from the human body. Some have been designed as just research devices, some have been available commercially, but have been withdrawn, and some are still available. Most, but not all, are based on the spontaneous EEG and the AER. Some have been designed to use properties of the ECG. Although useful, all of the discussed monitors have some shortcomings, and not all are 100% sensitive and specific to discriminate between consciousness and unconsciousness, and none correlate exactly with clinical states and levels of anaesthesia. The design of the commercial monitor, the Cerebral Function Monitor (CFM) was based on simple time domain measures already discussed [Maynard et al. 1969]. The CFM took the EEG from a single pair of parietal electrodes. The signal was amplified and passed through a band-pass filter and differentiator, which had the effect of accentuating the gain of the higher end of the 2–15 Hz pass band. The output of this specialised filter was integrated to produce a voltage output, which varied with time. It was plotted on a logarithmic scale. The trace on the paper gave an indication of the power of the EEG and the width of the line gave an indication of the signal’s variability. A schematic of an example of a CFM trace is shown in Figure 19.1(a). The CFM although useful did have its problems [Sechzer 1977]. When used to monitor depth of anaesthesia, the machine was shown to be unreliable, especially when using inhalational agents. The response is biphasic, as has already been discussed in chapter 18. Also burst suppression, as already discussed, is smoothed out by the action of the filtering in the CFM, so effectively the burst suppression can artificially elevate the readings producing a paradoxical rise in cerebral function [Sinha 2007] The machine was further developed into the Cerebral Function Analysing Monitor (CFAM)[Maynard 1984]. This machine produced two chart recorder outputs, as shown in Figure 19.1. There was a chart similar to the CFM trace, and also a chart that produced frequency domain data consisting of the EEG displayed as traditional EEG frequency bands.
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Jayawickreme, Eranda, et Sara Etz Mendonça. « Using Methods from Personality Psychology to Study Post-Traumatic Growth ». Dans Redesigning Research on Post-Traumatic Growth, 73–88. Oxford University Press, 2021. http://dx.doi.org/10.1093/med-psych/9780197507407.003.0005.
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This chapter discusses methodological approaches for examining the causality, accuracy, stability, and mechanisms of short-term adversity-driven change in samples drawn from different populations, each highly likely to be exposed to different forms of challenge and failure. This methodological work builds on Frazier et al.’s (2009) groundbreaking longitudinal study. The authors discuss the advantages of using longitudinal multimethod measurement burst designs and a profile approach utilizing a round-robin design, as well as a qualitative assessment. Each methodology promises to address novel questions concerning the perception, meta-perception, and development of character following challenge and failure. The chapter also examines individual difference factors, such as social support and cumulative life adversity, which may moderate this relationship. Given that participants from different populations likely differ in the amount of cumulative adversity they have experienced, the authors also examine the possibilities and limitations of lifetime adversity in acting as a catalyst for subsequent growth.
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Luong, Gloria, J. Doug Coatsworth et Sy-Miin Chow. « Post-Traumatic Growth in Later Adulthood ». Dans Redesigning Research on Post-Traumatic Growth, 105–22. Oxford University Press, 2021. http://dx.doi.org/10.1093/med-psych/9780197507407.003.0007.
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This chapter focuses on conceptual notions and methodological approaches for examining whether post-traumatic growth is possible in older adults, with an emphasis on individual and dyadic approaches. A majority of the literature to this point has focused on examining changes in the individual who experienced the traumatic event, but much less is known regarding how a partner or spouse responds to the traumatic event. This chapter discusses how the use of multimethod prospective longitudinal measurement burst designs can provide insights into this growth following a traumatic event. The authors discuss as an example the case when at least one partner is planning to transition into assisted living. An increasing number of individuals reaching old age must make the decision to transition into an assisted living or similar type of home. The use of multimethod prospective longitudinal designs enables the researcher to delineate the extent to which character virtues may change on different time scales in terms of state character virtues assessed in daily life (e.g., how altruistic a person is in a given moment or day) versus trait characteristics (e.g., how altruistic a person is, on average) and elucidate hypothesized transactional mechanisms (e.g., individual differences, dyadic, and contextual factors, such as experiences of daily stressors) that may promote or inhibit changes in character virtues.
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İsmail Tosun, Yildırım. « Asphalt Fill Strengthening of Free Slip Surfaces of Shale Slopes in Asphaltite Open Quarry : Stability Analysis of Free Sliding Surface for Wet Shale Slopes in Avgamasya Asphaltite Open Quarry No 2. Site ». Dans Slope Engineering [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94893.
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The stability analysis carried out by GEO5 software and uses free sliding analysis by wet and pore saturated weight charting provided the safety factor of 1.35. The safety precautions were followed by inclinometers and wire extensometer measurements. The other pore saturated asphalt bound shear box and unaxial test compression tests were resulted in the geotechnical and geoseismical data over sliding soil /shale inter surface quality and the characteristics of free rock falling risk and discontinuity distribution, sub crack density and distribution on stereo nets were determined. The research was firstly followed the perched water levels on geoseismical data over causing water burst or explosion of highly free mud and landslides. The hazardous rock falls over saturated soil and uncohesive rock explosions. The proposed study was secondly as strengthening methods such as asphalt mixing as precautious on shear stabilization and other wire mesh barriers anchored. The free sliding cracks was filled by asphalt and compressed for stabilization strengthening known as the characteristics of avoiding shear falls in the future. The unconditional expectations related to this study was also defined for this region such as the influence of the ground water, rock cracks and slope design, explosion exchange dynamics leading to landslide.
Actes de conférences sur le sujet "Measurement burst design"
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Gray, Cecelia, Thomas Oliva, Alexander Christakis, Marsha Rolle et Kristen Billiar. « Design of a versatile, inexpensive vessel burst pressure measurement device ». Dans 2009 IEEE 35th Annual Northeast Bioengineering Conference. IEEE, 2009. http://dx.doi.org/10.1109/nebc.2009.4967682.
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Rodriguez, Andres, Kevin Logan, James Nickles et Greg Carlson. « Enhanced Method for Dimensional Measurement of Oilfield Tubulars to Optimize Operations and Minimize Risk Factors ». Dans IADC/SPE International Drilling Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/208728-ms.
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Abstract Technological advances in the nondestructive evaluation of Oil Country Tubular Goods (OCTG) have brought about enhanced methods to minimize risk factors associated with the drilling or transport of oil and natural gas. This paper focuses on a multidimensional, nondestructive testing (NDT) inspection and measurement package combining wall thickness and outer diameter (OD) measurement data into a single inspection report per tubular. This method of dimensional measurement is performed on the front end of a project, providing end users with numerous benefits from a cost and time perspective, as well as the critical data needed to optimize operations. The package provides high-resolution inspection data for the manufacturer or end user, yielding higher precision burst and collapse strength predictions than previously available. Other benefits of this method include optimization of material placement in casing string design, estimation of cementing fluid volume, and downhole tool clearances among other applications. Confidence and safety levels of burst and collapse ratings are of particular interest to drilling engineers. The wall thickness variations and tubular eccentricity are measured using an automated, nondestructive ultrasonic testing system, utilizing compression wave transducers. The OD measurement is acquired using an automated, nondestructive laser-based testing system. Laser-based testing uses two laser-scan micrometers positioned horizontal to the tubular and 180° apart (Fig. 1). Each laser measures the distance between the tubular and the receiver. These two measurements are combined to calculate the tubular OD. The level of accuracy provided by this technology continues to push the industry forward with higher quality tubulars ranging from the mills to end users.
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Sundaramurthy, Aravind, Raj K. Gupta et Namas Chandra. « Design Considerations for Compression Gas Driven Shock Tube to Replicate Field Relevant Primary Blast Condition ». Dans ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63732.
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Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions. In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube. From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.
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Judge, John A., Joseph F. Vignola, Aldo A. J. Glean, Teresa J. Ryan, Chelsea E. Good, Peter M. Gugino, Steven S. Bishop et Mehrdad Soumekh. « Detection of Non-Metallic Cords Using Synthetic Aperture Acoustic Imaging ». Dans ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71102.
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Synthetic aperture acoustic (SAA) imaging is a technique for remotely obtaining information about the location, geometry, and mechanical properties of objects based on the way they scatter incident acoustic energy. Results are presented for an experimental investigation of the use of SAA imaging to detect non-metallic cords of different sizes laid in various configurations on the ground surface in an outdoor urban environment. Interest in this application of SAA stems from the fact that non-metallic cords are not readily detectable with synthetic aperture radar (SAR) and that the SAA imaging approach represents a relatively inexpensive alternative or supplement to SAR. The measurement system is comprised of a mobile acoustic transceiver (a speaker and microphone) that broadcasts a burst chirp with a bandwidth of 2–15 kHz. The recorded signal is used to form a two-dimensional image of the distribution of acoustic scatterers within the scene. For this study, five different diameters (2–15mm) of nylon cord laid on the ground were imaged in different configurations. These measurements were made in the presence of urban ambient noise of varying levels. The goal of this study was to identify the effect of environmental noise and other parameters on detectability. The results demonstrate that non-metallic cords can be detected acoustically if the angle to the transceiver path is sufficiently small.
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Zeinali, Hossein, Peter Toma et Ergun Kuru. « Near-Wall Turbulent Transport Knowledge for Suitable Flow Assurance Strategies ». Dans ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79996.
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Gas-liquid transportation from the deep ocean floor level to wellhead and, then, to platforms and land processing units is often impeded by wax and hydrates deposits; sand erosion and corrosion-related being frequently encountered. During the last decades it was shown that apparently different problems such as sand erosion and deposition-removal of paraffin during turbulent pipe transportation are the effect of near-wall flow transport related to burst-sweep specific turbulent activity. Coherent structures visualized as a sequence of (in) bursts and outburst sweep actions has already been suggested as an important factor for understanding aging of the paraffin deposit and the deposition-removal balance controlling the grow of deposit. This paper, using published models, investigates the effect of near-wall turbulence on removal of small-size particulate matter, first through direct measurement of burst activity, then, using fine sand and glass beads transported as moving bed during turbulent flow condition. Lack of experimental data for assessing the effect of turbulent liquid pipe flow on burst activity for removal of fines created challenging problems. Those include direct assessment of burst frequency and measurement of the rate of fine sand grading and on-line sampling and measuring the rate of fine removal during sand bed or lenticular deposits transportation. Laboratory work uses a Particle Image Velocimetry (PIV) instrument to observe and quantified the burst activity as it progresses from the pipe wall to the turbulent core flow. Experimental data are closely compared to existing literature models; in addition the present laboratory measurements allow for describing the dynamic of a burst as it evolves from the pipe wall to turbulent core regions. The frequency of burst removal is further compared with changing of size distribution during the sand bed-slurry transport stage of this work. Results obtained so far at the University of Alberta with the aid of an experimental loop designed and operated for observing and quantifying selective (size-density) radial-axial transportation of fines are discussed and summarized. It is suggested that the experimental data on fines removal and deposition, particularly related to near-turbulent structure activity, is important for understanding and mitigating a broad range of near-wall turbulent-related flow assurance problems.
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Brechan, B., S. Sangesland et S. Dale. « Improved Model for Tubular Burst ». Dans ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95819.
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Abstract Modern casing design can reduce significant amounts of CO2 and considerable cost per well [1]. Collapse design was modernized by ISO/API Technical committee 67, Sub Committee 5, Work Group 2b (ISO/API TC67/SC5/WG2b). Modernization of burst design has so far not had the same focus and only minor changes have been made. A new burst design model has been developed to add to the collapse prediction for a complete environmental and cost effective well design tool. It is based on the theories of Lubinski [2] (1975) and presents designs using “exact von Mises ellipsis” together with the Klever and Stewart ductile rupture model [3]. This paper presents the model developed for burst design and the improvement compared to current industry practice. Inspired by the current most accurate collapse prediction model [4], the modified burst model (prototype) is the first to consider actual wall thickness to predict a more accurate internal yield of OCTG (Oil Country Tubular Goods). Investigations show that the standard 12.5% wall thickness reduction for manufacturing tolerances may be obsolete. ISO 10400 offers physical measurements and statistics of tubular properties. Following the principals by WG2b applied with the Klever & Tamano collapse prediction, there is a set of data to be used for a specific batch of tubulars or they are deducted through large quantum of measurements; ensemble Probability Density Function (PDF). The value proposed as “ensemble PDF” for wall thickness is based on more than 10 000 measurements of tubulars from 11 vendors distributed over Electrical Weld (EW) and quenched and tempered (Q&T) qualities of miscellaneous sizes and grades. The batch specific value proposed is based on more modest numbers of specimens from 4 sources but offers “minimum measured wall thickness” for all the samples. Adding to the confidence of the final design is the automated ductile burst calculation, which is one of the latest contributions to burst modeling in the industry [4] [5] [6]. It is a useful aid for the design engineer to know the potential failure mode and the limit before loss of integrity. However, burst is limited to yield because exceeding this limit may lead to loss of the pipe’s effective diameter and eventually loss of integrity. Therefore, the ductile burst prediction is proposed as a visual aid only.
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Townsend, Todd, Will Moss, Dennis Heinisch, Kenneth Evans et Cecil Schandorf. « Advanced High Frequency In-Bit Vibration Measurement Including Independent, Spatially Separated Sensors for Proper Resolution of Vibration Components Including Lateral, Radial, and Tangential Acceleration ». Dans Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/208110-ms.
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Abstract Vibration measurement has become ubiquitous in drilling. Focus of drilling enhancement has expanded from traditional lateral and stick slip assessment to include torsional oscillations on motors, and high-frequency torsional oscillations (HFTO). Recent publications have highlighted the importance of these higher frequency measurements to analyze drilling dynamics and diagnose dysfunctions which can cause tool failures. A new vibration recorder will be presented which is capable of sampling at 2 kHz and higher to analyze non-linear transient dysfunctions. Most in-bit vibration measurement options utilize a single unsynchronized triaxial accelerometer and low speed gyro. This design practice inherits specific challenges to the measurement and prevents the ability to decouple lateral from angular acceleration. Use of two sets of symmetrically placed (180 degree opposing) accelerometers has been in practice, but design constraints limit this approach to larger bits. Utilization of a new, outer diameter (OD) mounted vibration recorder for slim hole bits/BHAs with multiple spatially separated triaxial accelerometers, and a high-speed precision gyro will be described and evaluated with a comparison to other commercially available options. Downhole vibration recorders have existed for over 20 years providing conventional drilling dynamics evaluation. These devices suffered from hardware limitations which constrained the customer to spaced out snapshots of time rather than continuous observation and required separate research modules to cover high frequency needs. This paper presents case studies utilizing a new vibration recorder which can cover these two customer needs in one device. Drilling Engineers desire a rapid turnaround macro view of synchronized downhole and surface data for offset well parameter optimization while research engineers desire a micro view with kilohertz range sample rate for a comprehensive understanding of all possible dysfunctions including HFTO, and high frequency shock, along with the capacity to research geology prediction techniques including fracture identification. Use of an advanced cloud-based software suite will be illustrated for a rapid high-level view of the full run with benchmarking capability of offset wells. Case study observations include stick slip identification covering 0 to above 600 rpm using a single gyroscope, and HFTO identification with accurate decoupling of tangential acceleration vs radial and lateral. Having the ability to satisfy both objectives with one device is new to the industry and presents a step change in capability. A new, advanced vibration recorder is detailed which includes synchronized, spatially separated triaxial accelerometers, a triaxial shock sensor, a highspeed triaxial gyroscope, and temperature sensors. With 5 gigabytes of high temperature flash memory, more than 2 kHz sample rate for burst data and 1s period for downhole processed data, logged downhole recordings can cover greater than 200 hrs of drilling and may be available for analysis within minutes from drilling completion.
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Watson, Mark, Artur J. Jaworski et Norman J. Wood. « The Application of Synthetic Jet Actuators for the Modification of the Characteristics of Separated Shear Layers ». Dans ASME 7th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2004. http://dx.doi.org/10.1115/esda2004-58561.
Texte intégralRésumé :
This paper presents an experimental investigation related to controlling the unsteady characteristics of the separated shear layers occurring over highly swept wings, and in particular focuses on application of synthetic jet actuators for modification of unsteady dynamic loading on the wing surface due to the phenomenon referred to as vortex breakdown (burst). In the post burst flow region the surface pressure measurements reveal the presence of certain characteristic spectral peaks that are thought to represent the presence of a spiralling filament of vorticity inside the expanded vortex that is known to be present in the burst flow over swept wings. This paper details an investigation into how the use of an array of 18 discrete synthetic jet actuators, distributed along the leading edge of a delta wing with a 60° sweep angle, can be used to alter the spectral content of this unsteadiness and reduce the level of unsteady pressure found in the post-burst region toward the wing trailing edge by up to 40%. Measurements of the surface pressure spectral distributions over the wing are presented together with PIV measurements of the vortex cross-section, conducted in the successive planes parallel to the wing trailing edge. Additional surface flow visualisation indicates that the effect of the actuators on the leading edge boundary layer is to induce local separation delays close to each actuator orifice, which introduce “ripples” into the shear layer as it separates. The results obtained are used to formulate an interpretative hypothesis attempting to explain the mechanisms responsible for modification of the spectral content and the level of excitation measured on the wing surface.
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Lance, Blake W., et Matthew D. Carlson. « Compact Heat Exchanger Semi-Circular Header Burst Pressure and Strain Validation ». Dans ASME Turbo Expo 2019 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91772.
Texte intégralRésumé :
Abstract Compact heat exchangers for supercritical CO2 (sCO2) service are often designed with external, semi-circular headers. Their design is governed by the ASME Boiler & Pressure Vessel Code (BPVC) whose equations were typically derived by following Castigliano’s Theorems. However, there are no known validation experiments to support their claims of pressure rating or burst pressure predictions nor is there much information about how and where failures occur. This work includes high pressure bursting of three semi-circular header prototypes for the validation of three aspects: (1) burst pressure predictions from the BPVC, (2) strain predictions from Finite Element Analysis (FEA), and (3) deformation from FEA. The header prototypes were designed with geometry and weld specifications from the BPVC Section VIII Division 1, a design pressure typical of sCO2 service of 3,900 psi (26.9 MPa), and were built with 316 SS. Repeating the test in triplicate allows for greater confidence in the experimental results and enables data averaging. Burst pressure predictions are compared with experimental results for accuracy assessment. The prototypes are analyzed to understand their failure mechanism and locations. Experimental strain and deformation measurements were obtained optically with Digital Image Correlation (DIC). This technique allows strain to be measured in two dimensions and even allows for deformation measurements, all without contacting the prototype. Eight cameras are used for full coverage of both headers on the prototypes. The rich data from this technique are an excellent validation source for FEA strain and deformation predictions. Experimental data and simulation predictions are compared to assess simulation accuracy.
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Wiseall, S. S., R. Thomas et P. Butler. « The Application of a Laser Doppler Anemometer system to a high speed multi-stage Compressor using a Digital Burst Correlator ». Dans Photon Correlation and Scattering. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/pcs.1996.tha.1.
Texte intégralRésumé :
Two component LDA velocity measurements have been made in three axial planes: just downstream of the Inlet Guide Vanes, (IGVs); the rotor and stators of a high speed aeroengine Compressor. At each axial stage circumferential measurements over a 22.5 degree arc were made in 0.25 degree interval steps at 21 radial heights between 2% and 98 %. The latter corresponds to high quality velocity measurement data less than 0.5 mm from the rig window. Overall, the data collection corresponds to over 10,000 2D velocity measurements with between 3-7000 velocity samples per spatial location. Some of these data are illustrated in the 3D contour plots shown of the measured IGV velocity magnitude and the flow angle. These data and other similar data at the other axial locations have been used to help develop new blade designs and validate Computational Fluid Dynamic codes. The sharp IGV wakes were resolved in 0.05 degree angular steps, each wake being some 0.4 degrees wide. The results show the very severe velocity gradient through the wake and the significant variation in flow angle in the boundary layer, (up to 20 % annulus height and above 80 % annulus height). The stability of the LDA system and the measurement rig was such that circumferential velocity profiles measured 12 days apart deviated at most by less than 0.5 %. Comparison with conventional instrumentation in measurement regions where this was valid has shown agreement to within 0.2 %.