Academic literature on the topic 'Identification (presque)-faible'
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Journal articles on the topic "Identification (presque)-faible"
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Smith, Dale B., Edward A. Woody, Margaret Richardson, Herbert L. Olsen, and Don B. Blakeslee. "A Device for the Intraoperative Identification of the Recurrent Laryngeal Nerve in Piglets." Otolaryngology–Head and Neck Surgery 100, no. 2 (February 1989): 137–45. http://dx.doi.org/10.1177/019459988910000210.
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The recurrent laryngeal nerve (RLN) is one of the most frequently injured nerves in head and neck surgery. Routine identification of the RLN during thyroid surgery has reduced the injury rate from 10% to less than 4%. Difficulty in identification of the RLN contributes to this surgical morbidity. Devices previously used for intraoperative identification of the RLN have failed to achieve the simplicity and reliability necessary for clinical use. This animal study uses a simple double-ballooned endotracheal tube and pressure transducer system, which assists intraoperative RLN identification through nerve stimulation and graphic documentation of vocal fold (VF) motion. Iatrogenic injury is demonstrated by a dampened stimulation-pressure tracing. The RLNs of three piglets were injured and examined, and the degree of injury was correlated with perioperative nerve stimulation patterns. The piglet proved to be an adequate model for laryngeal research. An FDA-approved multi-institutional prospective human study using this system of Identification of the RLN is in progress.
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Pan, Qing, Ming Hui Huang, and Yi Bo Li. "Modeling and Identification of Friction Behaviors of Hydraulic Forging Press Machine." Applied Mechanics and Materials 328 (June 2013): 77–83. http://dx.doi.org/10.4028/www.scientific.net/amm.328.77.
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A novel modified LuGre friction model is proposed by taking pressure of the cylinders into consideration. And a practical identification method to estimate the parameters associated with the modified friction model is presented. The validity of the modified model is investigated experimentally. It is shown that the modified LuGre model can demonstrate the comprehensive friction behaviors of the forging machine with a fairly good accuracy.
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Connolly, F. T., and A. E. Yagle. "Modeling and Identification of the Combustion Pressure Process in Internal Combustion Engines: II—Experimental Results." Journal of Engineering for Gas Turbines and Power 115, no. 4 (October 1, 1993): 801–9. http://dx.doi.org/10.1115/1.2906778.
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In Connolly and Yagle (1992, 1993) we presented a new model relating cylinder combustion pressure to crankshaft angular velocity in an internal combustion engine, primarily the fluctuations in velocity near the cylinder firing frequency. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a nonlinear differential equation becomes a linear first-order differential equation. Second, a new stochastic model for combustion pressure uses the sum of a deterministic waveform and a raised-cosine window amplitude-modulated by a Bernoulli-Gaussian random sequence, parametrizing the pressure by the sample modulating sequence. This results in a state equation for the square of angular velocity sampled every combustion, with the modulating sequence as input. Third, the inverse problem of reconstructing pressure from noisy angular velocity measurements was formulated as a state-space deconvolution problem, and solved using a Kalman-filter-based deconvolution algorithm. Simulation results in Connolly and Yagle (1992, 1993) show that the parametrized pressure can be deconvolved at low to moderate noise levels, and combustion misfires detected, all in real time. This paper presents and discusses experimental results that confirm this model, at least at the relatively low-speed, low-to-moderate load operating conditions analyzed. They show that cyclic combustion pressure variation is fairly well modeled and may be directly estimated from angular velocity measurements. They also show that the deconvolution algorithm is able to detect misfires and possibly classify their severity. Since the experimental data are taken from an actual V-6 automobile engine, and the algorithms are simple enough to be implemented in real time, these results are directly applicable to real-world combustion pressure identification.
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Vaira, Pasquale, Michela Camorcia, Tiziana Palladino, Matteo Velardo, and Giorgio Capogna. "Differentiating False Loss of Resistance from True Loss of Resistance While Performing the Epidural Block with the CompuFlo® Epidural Instrument." Anesthesiology Research and Practice 2019 (February 3, 2019): 1–4. http://dx.doi.org/10.1155/2019/5185901.
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Background. The occurrence of false losses of resistance may be one of the reasons for inadequate or failed epidural block. A CompuFlo® epidural instrument has been introduced to measure the pressure of human tissues in real time at the orifice of a needle and has been used as a tool to identify the epidural space. The aim of this study was to investigate the sensitivity and the specificity of the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance encountered during the epidural space identification procedure. Method. We performed epidural block with the CompuFlo® epidural instrument in 120 healthy women who requested labor epidural analgesia. The epidural needle was considered to have reached the epidural space when an increase in pressure (accompanied by an increase in the pitch of the audible tone) was followed by a sudden and sustained drop in pressure for more than 5 seconds accompanied by a sudden decrease in the pitch of the audible tone, resulting in the formation of a low and stable pressure plateau. We evaluate the sensitivity, specificity, and positive and negative predictive values of the ability of CompuFlo® recordings to correctly identify the true LOR from the false LOR. Results. The drop in pressure associated with the epidural space identification was significantly greater than that recorded after the false loss of resistance (73% vs 33%) (P=0.000001). The sensitivity was 0.83, and the AUC was 0.82. Discussion. We have confirmed the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance and established its specificity and sensitivity. Conclusion. An easier identification of dubious losses of resistance during the epidural procedure is essential to reduce the number of epidural attempts and/or needle reinsertions with the potential of a reduced risk of accidental dural puncture especially in difficult cases or when the procedure is performed by trainees.
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Shin, Young-Suk. "Monitoring Personalized Trait Using Oscillometric Arterial Blood Pressure Measurements." Journal of Applied Mathematics 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/591252.
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The blood pressure patterns obtained from a linearly or stepwise deflating cuff exhibit personalized traits, such as fairly uniform peak patterns and regular beat geometry; it can support the diagnosis and monitoring of hypertensive patients with reduced sensitivity to fluctuations in Blood Pressure (BP) over time. Monitoring of personalized trait in Oscillometric Arterial Blood Pressure Measurements (OABPM) uses the Linear Discriminant Analysis (LDA) algorithm. The representation of personalized traits with features from the oscillometric waveforms using LDA algorithm includes four phases. Data collection consists of blood pressure data using auscultatory measurements and pressure oscillations data obtained from the oscillometric method. Preprocessing involves the normalization of various sized oscillometric waveforms to a uniform size. Feature extraction involves the use of features from oscillometric amplitudes, and trait identification involves the use of the LDA algorithm. In this paper, it presents a novel OABPM-based blood pressure monitoring system that can monitor personalized blood pressure pattern. Our approach can reduce sensitivity to fluctuations in blood pressure with the features extracted from the whole area in oscillometric arterial blood pressure measurement. Therefore this technique offers reliable blood pressure patterns. This study provides a cornerstone for the diagnosis and management of hypertension in the foreseeable future.
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ISLAM, M. J., S. SWADDIWUDHIPONG, and Z. S. LIU. "PENETRATION OF CONCRETE TARGETS USING A MODIFIED HOLMQUIST–JOHNSON–COOK MATERIAL MODEL." International Journal of Computational Methods 09, no. 04 (December 2012): 1250056. http://dx.doi.org/10.1142/s0219876212500569.
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For concrete target penetration and/or perforation simulation, the Holmquist–Johnson–Cook (HJC) material model is widely used as concrete material model. However, the strain rate expression of the model has failed to explain the sudden increase in concrete strength at high strain rates. The pressure-volume relationship of the HJC model is complex and requires a large number of material constants. In this study, a modified Holmquist–Johnson–Cook (HJC) model is proposed for concrete material under high velocity impact. The modification involves simplification and improvement of the strain rate expression and pressure-volume relationship. Material parameters identification procedure for the MHJC model is also elaborated. The numerical simulations using the proposed model show a good agreement with experimental observations, especially, on the residual velocities, penetration depths and failure patterns of the target plates. These validate the applicability of the MHJC model for high velocity projectile impact studies for concrete.
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Van Hemelrijck, Mathias, Michelle Frank, Annelies S. Zinkernagel, Ronny Buechel, Juri Sromicki, Markus J. Wilhelm, Holger Klein, Barbara Hasse, and Carlos A. Mestres. "Sternectomy for Candida albicans sternal osteomyelitis after left ventricular assist device implantation." Indian Journal of Thoracic and Cardiovascular Surgery 37, no. 5 (February 17, 2021): 573–76. http://dx.doi.org/10.1007/s12055-021-01144-x.
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AbstractFungal osteomyelitis is an uncommon complication after cardiac surgery and associated with high mortality. A case of Candida albicans and Staphylococcus epidermidis osteomyelitis with device infection after implantation of a left ventricular assist device in a 60-year-old male patient is presented here. After clinical identification and confirmation with microbiological examinations and fluorodeoxyglucose positron emission tomography (FDG-PET) scan, debridement was performed. Surgical specimens grew C. albicans and S. epidermidis. Fluconazole, daptomycin, and negative pressure wound therapy were initiated, but failed to achieve healing. Total sternectomy and pectoralis flap reconstruction were performed. There was no recurrent infection for C. albicans on a prolonged antifungal regime. The combination of antifungal therapy and aggressive surgical debridement may be useful to control fungal osteomyelitis.
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Liebenberg, Leon, John R. Thome, and Josua P. Meyer. "Flow Visualization and Flow Pattern Identification With Power Spectral Density Distributions of Pressure Traces During Refrigerant Condensation in Smooth and Microfin Tubes." Journal of Heat Transfer 127, no. 3 (March 1, 2005): 209–20. http://dx.doi.org/10.1115/1.1857942.
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This paper presents a flow pattern identifier of the prevailing flow regime during refrigerant condensation inside smooth- and microfin tubes. The power spectral density distribution of the fluctuating condensing pressure signal was used to identify the prevailing flow regime, as opposed to the traditional (and subjective) use of visual-only methods, and/or smooth-tube flow regime maps. The prevailing flow regime was observed by using digital cameras and was validated with the use of the conventional smooth-tube flow regime transition criteria, as well as a new flow regime map for microfin-tube condensation. Experimental work was conducted for condensing refrigerants R-22, R-407C, and R-134a at an average saturation temperature of 40°C with mass fluxes ranging from 300–800 kg/m2 s, and with vapor qualities ranging from 0.05–0.15 at condenser outlet to 0.85–0.95 at condenser inlet. Tests were conducted with one smooth-tube condenser and three microfin-tube condensers (with helix angles of 10°, 18°, and 37° respectively). The power spectral density distributions of the condensing pressure signals distinguish the annular and intermittent (slug and plug) flows. A very low resonant frequency (<40 Hz) and low power spectral density amplitude of the pressure oscillation denoted stratified and wavy flows. As the annular flow regime was approached, the oscillations became larger and their frequencies increased (typically 40–120 Hz). Intermittent flow showed the most distinct character of all flow regimes. Its trace consisted of large amplitude pressure pulses occurring at fairly constant frequencies (approximately 50, 60, 80, 100, and 120 Hz). As the transition from intermittent to annular flow began, the pressure fluctuations became less regular and the amplitude dropped sharply.
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Sun, Y., and H. Gewirtz. "Estimation of intramyocardial pressure and coronary blood flow distribution." American Journal of Physiology-Heart and Circulatory Physiology 255, no. 3 (September 1, 1988): H664—H672. http://dx.doi.org/10.1152/ajpheart.1988.255.3.h664.
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To characterize the intramyocardial pressure (IMP) and coronary blood flow distribution in a stenosed coronary circulation, we compared four analog circuits for modeling coronary impedance. The resistor (R)-diode (D) model simulates vascular collapse, and the capacitor (C) simulates compliance effect. Identification of the best model and magnitudes of the endocardial and epicardial IMPs (IMPendo and IMPepi) was done retrospectively using data from studies in 28 anesthetized swine. Performance evaluation was based on comparison of model predicted vs. observed coronary distal pressure (DP) waveforms and endocardial-to-epicardial (endo-epi) flow ratios as determined by radiolabeled microspheres. The R-D-C model gave the best performance at IMPendo = 1.1 times left ventricular pressure (LVP), and IMPepi = 0.1.LVP + 15 mmHg; with good fit to DP (r = 0.98, slope of regression line = 1.0) and estimates of endo-epi flow ratio (r = 0.78, slope = 1.01, P less than 0.02, SEE = 0.21, n = 139). The R-D model gave comparable results even though capacitance was omitted. Although R-C and R models predicted distal coronary pressure well, they failed to predict endo-epi flow ratios (r less than 0.50). The R-D-C and R-D models were applied in seven prospective studies. Both models generated reasonable estimates of endo-epi flow distribution (r = 0.78, n = 50). Thus the R-D-C or R-D models of the stenosed coronary circulation can be used to provide reliable estimates of transmural blood flow distribution.
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Pavelchak, Nicholas, Ronald P. DePersis, Matthew London, Rachel Stricof, Margaret Oxtoby, George DiFerdinando, and Elizabeth Marshall. "Identification of Factors That Disrupt Negative Air Pressurization of Respiratory Isolation Rooms." Infection Control & Hospital Epidemiology 21, no. 3 (March 2000): 191–95. http://dx.doi.org/10.1086/501742.
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AbstractObjectives:To investigate the airflow characteristics of respiratory isolation rooms (IRs) and to evaluate the use of visible smoke as a monitoring tool.Methods:Industrial hygienists from the New York State Department of Health evaluated 140 designated IRs in 38 facilities within New York State during 1992 to 1998. The rooms were located in the following settings: hospitals (59%), correctional facilities (40%), and nursing homes (1%). Each room was tested with visible smoke for directional airflow into the patient room (ie, negative air pressure relative to adjacent areas). Information was obtained on each facility's policies and procedures for maintaining and monitoring the operation of the IRs.Results:Inappropriate outward airflow was observed in 38% of the IRs tested. Multiple factors were associated with outward airflow direction, including ventilation systems not balanced (54% of failed rooms), shared anterooms (14%), turbulent airflow patterns (11%), and automated control system inaccuracies (10%). Of the 140 tested rooms, 38 (27%) had either electrical or mechanical devices to monitor air pressurization continuously. The direction of airflow at the door to 50% (19/38) of these rooms was the opposite of that indicated by the continuous monitors at the time of our evaluations. The inability of continuous monitors to indicate the direction of airflow was associated with instrument limitations (74%) and malfunction of the devices (26%). In one facility, daily smoke testing by infection control staff was responsible for identifying the malfunction of a state-of-the-art computerized ventilation monitoring and control system in a room housing a patient infectious with drug-resistant tuberculosis.Conclusion:A substantial percentage of IRs did not meet the negative air pressure criterion. These failures were associated with a variety of characteristics in the design and operation of the IRs. Our findings indicate that a balanced ventilation system does not guarantee inward airflow direction. Devices that continuously monitor and, in some cases, control the pressurization of IRs had poor reliability. This study demonstrates the utility of using visible smoke for testing directional airflow of IRs, whether or not continuous monitors are used. Institutional tuberculosis control programs should include provisions for appropriate monitoring and maintenance of IR systems on a frequent basis, including the use of visible smoke.
Dissertations / Theses on the topic "Identification (presque)-faible"
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Antoine, Bertille. "Gérer le risque d'échantillonnage en économétrie financière : modélisation et contrôle." Thèse, 2007. http://hdl.handle.net/1866/1963.
Full textBooks on the topic "Identification (presque)-faible"
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Lori, Turnbull. Part II Institutions and Constitutional Change, B The Parliamentary System, Ch.8 Political Institutions in Canada in a New Era. Oxford University Press, 2017. http://dx.doi.org/10.1093/law/9780190664817.003.0008.
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This chapter examines the meaning and significance of the parliamentary reform package introduced by Prime Minister Justin Trudeau’s government in 2015. The proposed measures address themes that have been part of democratic reform agendas for many years, and most of them can be fairly described as low-hanging fruit. The one that stands out from the rest is the Trudeau government’s approach to appointments. Historically, Prime Ministers have made appointments to the Senate, the Supreme Court, and other positions of profile and authority with little to no restrictions on their discretion. The Trudeau government’s creation of independent advisory boards to preside over appointments throughout federal government institutions, and the identification of specified criteria to guide these appointments, represents a major departure from historic practice and a potentially significant shift away from the concentration of power in the hands of the political Executive.
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White, Ismail K., and Chryl N. Laird. Steadfast Democrats. Princeton University Press, 2020. http://dx.doi.org/10.23943/princeton/9780691199511.001.0001.
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Black Americans are by far the most unified racial group in American electoral politics, with 80 to 90 percent identifying as Democrats—a surprising figure given that nearly a third now also identify as ideologically conservative, up from less than 10 percent in the 1970s. Why has ideological change failed to push more black Americans into the Republican Party? This book answers this question with a pathbreaking new theory that foregrounds the specificity of the black American experience and illuminates social pressure as the key element of black Americans' unwavering support for the Democratic Party. The book argues that the roots of black political unity were established through the adversities of slavery and segregation, when black Americans forged uniquely strong social bonds for survival and resistance. It explains how these tight communities have continued to produce and enforce political norms—including Democratic Party identification in the post-Civil Rights era. The social experience of race for black Americans is thus fundamental to their political choices. Black voters are uniquely influenced by the social expectations of other black Americans to prioritize the group's ongoing struggle for freedom and equality. When navigating the choice of supporting a political party, this social expectation translates into affiliation with the Democratic Party. The book explores where and how black political norms are enforced, what this means for the future of black politics, and how this framework can be used to understand the electoral behavior of other communities.
Conference papers on the topic "Identification (presque)-faible"
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Ellis, Fred V. "Inferior Material Failures." In ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-2240.
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Three failures due to inferior material are discussed. In all cases, the specified material was 2-1/4 Cr-1 Mo and the installed material was carbon steel. A carbon steel girth weld in a hot reheat steam line failed after approximately 102,000 hours of service. The fracture was in the weld metal adjacent to the fusion interface. Creep rupture tests were performed using all weld metal and weldment specimens. The weldment life was approximately twice that of the all weld metal specimen, consistent with the effect of specimen size and oxidation on rupture life. The weldment fracture was in the weld metal adjacent to the fusion interface. The second failure was a main steam line drain failure. Based on safety considerations and as a corrective action, alloy analysis (positive material identification) was performed at three units on approximately 75 different high temperature drain lines. Inferior materials were found in straight pipes, elbows, and valves. The last series of failures were in the stub tubing at the reheat header installed by the OEM and in a superheat tube installed by the utility.
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Poggianti, Alessandro, Massimo Forni, Barbara Ferrucci, Riccardo Scipinotti, Didier De Bruyn, Bong Yoo, Silvia De Grandis, Maria Gabriella Castellano, Alberto Dusi, and Elena Manzoni. "SILER Project: Design of the Seismic Isolators." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29010.
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This paper describes the SILER (Seismic-Initiated event risk mitigation in LEad-cooled Reactors) Project results obtained so far in the design of the seismic isolation system of two nuclear power plants: the ELSY configuration for the LFR (Lead-Cooled Fast Reactor) design and the MYRRHA configuration for the accelerator-driven systems (ADS). The seismic protection of the nuclear buildings by means of seismic isolation has been chosen in order to minimize changes to the standard design of the civil works and internal components of the Nuclear Power Plant. The work led to the identification of the optimal design solution, in terms of type and location of seismic devices, to achieve compliance to the floor response acceleration spectra in horizontal and vertical direction, with levels of horizontal displacements not exceeding the maximum acceptable values for structural and non-structural elements. The isolators studied in the project are of the type elastomeric, both High Damping Rubber Bearings and Lead Rubber Bearings; moreover the adoption of a fail-safe system to limit the horizontal isolator deformation in case of beyond design earthquakes is studied.
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McGuffie, Sean, and Nathan Barkley. "A Case Study for Using Engineering Judgement When Analyzing Finite Element Results." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21643.
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Abstract The authors were tasked with designing and fabricating a thick walled (t > 4.5″) ASME Division 2 – Class 2 separator vessel. Due to its service requirements, the vessel is to be regularly hydrotested at 18.87 MPa (2,737 psig). Linear-elastic finite element (FE) evaluations of the vessel indicated that it passed all required Code checks, including the hydrotest check specified in Section VIII, Division 2, Paragraph 4.1.6.2. To develop a greater understanding of the advantages and disadvantages of each method, the FE analyst on the project routinely reanalyzes vessels that have been evaluated per the linear-elastic procedures of Part 5 of the ASME Section VIII, Division 2 Code with the nonlinear procedures also specified in Part 5. This practice allows for direct comparisons of the linear and nonlinear results and for identification of situations where nonlinear analyses could provide benefit. Such an analysis was performed on this vessel under the hydro-static test condition. However, this analysis failed due to solver failure / gross instability (plastic collapse) before the full hydro-static load was applied. The solver failure was confirmed and repeated in multiple FE packages. This presented a conundrum for the authors: should the linear-elastic results be accepted since the vessel passed the linear evaluations, or should they be invalidated since the nonlinear evaluations indicated that failure could occur during a hydrotest, which given the vessel’s operations, will occur frequently? This paper discusses the additional evaluations that were required to establish confidence that the vessel could be successfully hydrotested when fabricated. These included both the Code specified evaluations, and evaluations that allowed engineering judgement to be applied to the design.
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McKenzie, F., R. J. Smith, F. Scenini, and A. H. Sherry. "Characterisation of A508 Steel Cleavage Initiation Sites and Local Plasticity Using Surface Matching Technique." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97735.
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Cleavage fracture in ferritic pressure vessel steels is preceded by local plastic deformation that initiates micro-cracks at carbides or second phase particles within the highly stressed region ahead of a crack tip. The objective of this study is to locate initiation sites of failed Compact Tension fracture mechanics specimens, tested at temperatures within the lower ductile to brittle transition region. A surface matching approach was developed to identify regions of local plastic deformation on the fracture surfaces of tested specimens, using confocal microscopy to acquire accurately mapped topographic images of both fractured surfaces, and then subtracting each pair of images in a virtual environment. This methodology is conceptually similar to the fracture surface topography analysis (FRASTA) technique but uses a home developed MATLAB software based on image correlation. The residual mismatch (interference) between the two datasets was used to identify the regions of local plasticity on both fracture surfaces of each test specimen studied that is believed to be associated with the cleavage initiation sites. The size and location of the localised plasticity was found to be consistent with scanning electron microscopy observations of cleavage initiation sites located directly ahead of the fatigue pre-crack tips in tested specimens. Finite element modelling was used to identify the magnitude of stress at the identified regions of cleavage initiation for the specimens studied, providing new insights into the mechanism of cleavage initiation in the lower transition region. This study suggests that this is a promising methodology for the identification of the initiation sites of cleavage fracture.
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Moinereau, Dominique, Patrick Le Delliou, Elisabeth Keim, and Tomas Nicak. "STYLE Project: A Large Scale Ductile Tearing Experiment on a Cladded Ferritic Pipe." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28077.
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Within the framework of the FP7 European project STYLE, a large scale experiment has been performed at EDF on a cladded ferritic pipe. The objective of such an experiment was to investigate transferability of material properties from small specimens to large scale components. The large scale experiment involves applying 4-point bending under displacement control at room temperature to a clad ferritic steel pipe with an internal surface crack. The goal of the experiment is to initiate ductile crack growth and track the resulting stable crack growth until the surface flaw fails by producing a through-wall crack. The test specimen is representative from a surge line consisting of a clad ferritic pipe with an outer diameter of 420 mm, length of 520 mm, and base metal wall thickness of 31 mm, with an internal austenitic stainless steel cladding layer of thickness 5 mm. The base metal is a low alloy 20MnMoNi55 steel (corresponding to the specifications of an SA 508 Grade 3, Class 1 steel), and the necessary extensions are made of a high strength ferritic steel. A wide range of instrumentation was implemented to provide data for mock-up behavior understanding and detect the ductile tearing initiation during the test. The test has been conducted with full success on the EDF 4 point bending test facility. After the experiment, samples have been taken from the mock-up for full SEM fractographic examinations of the fracture surface for identification of failure modes. The present paper describes the large scale experiment and presents the main experimental results and data. A synthesis of SEM fractographic examinations is also presented, to better understand the rupture behavior during the test.
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Mazur, Zdzislaw, Rafael Garci´a-Illescas, Jorge Aguirre-Romano, and Norberto Pe´rez-Rodri´guez. "Last-Stage Blade Failure Evaluation." In ASME 2007 Power Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/power2007-22010.
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A last stage turbine blades failure was experienced in two units of 660 MW. These units have one high-pressure turbine and two tandem-compound low-pressure turbines with 44-inch last-stage blades. The blades that failed were in a low pressure (LP) turbine connected to the high pressure (HP) turbine (LP1) and in LP turbine connected to the generator (LP2). The failed blades had cracks in their roots initiating at the trailing edge, concave side of the steeple outermost fillet radius. Laboratory evaluation of the cracking indicates the failure mechanism to be high cycle fatigue (HCF). The last-stage blades failure evaluation was carried out. The investigation included a metallographic analysis of the cracked blades, natural frequency test and analysis, blade stress analysis, unit’s operation parameters and history of events analysis, fracture mechanics and crack propagation analysis. This paper provides an overview of this failure investigation, which led to the identification of the blades torsional vibrations near 120 Hz and some operation periods with low load low vacuum as the primary contribution to the observed failure.
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Wang, Jinli, Fuyuan Yang, Minggao Ouyang, and Ying Huang. "A Research on Engine Phase and Speed Estimation Method Based on Cylinder Pressure Sensor." In ASME 2013 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icef2013-19025.
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Cylinder pressure based combustion state control is a direction that has drawn much attention in the field of internal combustion engine control, especially in the field of diesel HCCI (Homogeneous Charge Compression Ignition) research. In-cylinder pressure sensors have the potential to diagnose or even replace many traditional sensors, including camshaft and crankshaft sensors. This paper did research on engine synchronization method based on in-cylinder pressure signal. The research was based on a 4-cylinder high pressure common rail diesel engine equipped with 4 PSG (Pressure Sensor Glow Plug) type piezo-resistance cylinder pressure sensors, intended for HCCI research. Through theoretical analysis and experimental proof, methods and models for cylinder identification, engine phase estimation and engine speed estimation are given and further verified by experiments. Results show that cylinder pressure sensor could be used to identify cylinder instead of cam shaft sensor. The models for engine phase and speed estimation have been proved to have precision of 3° crank angle and 4.6rpm, respectively. The precision of engine phase and speed estimation provides a possibility for the engine to run if the crankshaft sensor fails, but more researches have to be carried out with respect to crankshaft sensor replacement.
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Morgans, Aimee S., and Ann P. Dowling. "Model-Based Control of Combustion Instabilities." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68897.
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Model-based control has been successfully implemented on an atmospheric pressure lean premixed combustion rig. The rig incorporated a pressure transducer in the combustor to provide a sensor measurement, with actuation provided by a fuel valve. Controller design was based on experimental measurement of the open loop transfer function. This was achieved using a valve input signal which was the sum of an identification signal and a control signal from an empirical controller to eliminate the non-linear limit cycle. The transfer function was measured for the main instability occurring at a variety of operating conditions, and was found to be fairly similar in all cases. Using Nyquist and H∞-loop shaping techniques, several robust controllers were designed, based on a mathematical approximation to the measured transfer function. These were implemented experimentally on the rig, and were found to stabilise it under a variety of operating conditions, with a greater reduction in the pressure spectrum than had been achieved by the empirical controller.
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Haque, Mohammad Shafinul, and Calvin M. Stewart. "Modeling the Creep Deformation, Damage, and Rupture of Hastelloy X Using MPC Omega, Theta, and Sin-Hyperbolic Models." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63029.
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Combined cycle power plants components such as steam pipe work, pressure vessels, boilers, heat exchangers, and gas turbine disks, etc. are exposed to elevated temperature and pressure operation conditions for longer durations. Components may fail within the elastic limit due to a time dependent deformation and damage mechanism called creep. Creep prediction models are used to determine the state of these components and to schedule optimum inspection, maintenance, and replacement intervals. In this study, the deformation, damage, and life of Hastelloy X is characterized using three recently developed models; the Omega, Theta projection, and Sin-hyperbolic models. An analysis is performed to compare the models in terms of accuracy, assumptions, constant identification techniques, flexibility in use, and limitations. The influence that final creep strain has on Theta and Omega model is discussed. Sixteen tests were performed at four different configurations of stress (2.1–36.5 ksi) and temperature (1200–1800°F). In the experimental data, Hastelloy X does not exhibit the primary stage. In this study, the secondary and tertiary creep stages are modeled. Creep deformation and rupture life data is used to optimize the constants for the three models. Predictions using these models are compared with experimental data. It is found that the novel Sin-hyperbolic model better fits the experimental data, and is easier to apply. The Omega model predicts longer life than the Sinh and the Theta Projection model. The rupture life prediction of the Theta projection model is the worst due to dependence on the critical creep strain rate. It is observed that the Hastelloy X final creep strain depends on stress and temperature; this leads to a less accurate critical creep strain rate prediction resulting in inaccurate rupture life predictions for the Theta projection model. The analytical damage of the Omega model exhibits a linear evolution with time while the Sinh model show a more realistic elliptical creep damage evolution with time. A process to determine the constants of all the models is clearly described. The dependence of the trajectory of the creep curves with respect to the constants is discussed in detail. An analytical derivation of each model is provided. Predictions of these three models show that the Sinh model produces a better creep deformation curve by normalizing the experimental creep strain rate data. It is found that overall the Sinh model offers more flexibility, prediction accuracy, and is easier to apply.
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Lamouroux, Jean, Stéphane Richard, Quentin Malé, Gabriel Staffelbach, Antoine Dauptain, and Antony Misdariis. "On the Combination of Large Eddy Simulation and Phenomenological Soot Modelling to Calculate the Smoke Index From Aero-Engines Over a Large Range of Operating Conditions." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64262.
Full textAbstract:
Nowadays, models predicting soot emissions are, neither able to describe correctly fine effects of technological changes on sooting trends nor sufficiently validated at relevant operating conditions to match design office quantification needs. Yet, phenomenological descriptions of soot formation, containing key ingredients for soot modeling exist in the literature, such as the well-known Leung et al. model (Combust Flame 1991). This approach indeed includes contributions of nucleation, surface growth, coagulation, oxidation and thermophoretic transport of soot. When blindly applied to aeronautical combustors for different operating conditions, this model fails to hierarchize operating points compared to experimental measurements. The objective of this work is to propose an extension of the Leung model, including an identification of its constants over a wide range of condition relevant of gas turbines operation. Today, the identification process can hardly be based on laboratory flames since few detailed experimental data are available for heavy-fuels at high pressure. Thus, it is decided to directly target smoke number values measured at the engine exhaust for a variety of combustors and operating conditions from idling to take-off. A Large Eddy Simulation approach is retained for its intrinsic ability to reproduce finely unsteady behavior, mixing and intermittency. In this framework, The Leung model for soot is coupled to the TFLES model for combustion. It is shown that pressure-sensitive laws for the modelling constant of the soot surface chemistry are sufficient to reproduce engine emissions. Grid convergence is carried out to verify the robustness of the proposed approach. Several cases are then computed blindly to assess the prediction capabilities of the extended model. This study paves the way for the systematic use of a high fidelity tool solution in design office constraints for combustion chamber development.