Academic literature on the topic 'Potential drop techniques'
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Journal articles on the topic "Potential drop techniques"
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Li, Yuting, Fangji Gan, Zhengjun Wan, Junbi Liao, and Wenqiang Li. "Novel Method for Sizing Metallic Bottom Crack Depth Using Multi-frequency Alternating Current Potential Drop Technique." Measurement Science Review 15, no. 5 (October 1, 2015): 268. http://dx.doi.org/10.1515/msr-2015-0037.
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Abstract Potential drop techniques are of two types: the direct current potential drop (DCPD) technique and alternating current potential drop (ACPD) technique, and both of them are used in nondestructive testing. ACPD, as a kind of valid method in sizing metal cracks, has been applied to evaluate metal structures. However, our review of most available approaches revealed that some improvements can be done in measuring depth of metal bottom crack by means of ACPD, such as accuracy and sensitivity of shallow crack. This paper studied a novel method which utilized the slope of voltage ratio-frequency curve to solve bottom crack depth by using a simple mathematic equation based on finite element analysis. It is found that voltage ratio varies linearly with frequency in the range of 5-15 Hz; this range is slightly higher than the equivalent frequency and lower than semi-permeable frequency. Simulation and experiment show that the novel method can measure the bottom crack depth accurately.
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Graça, Angélica, Lídia Gonçalves, Sara Raposo, Helena Ribeiro, and Joana Marto. "Useful In Vitro Techniques to Evaluate the Mucoadhesive Properties of Hyaluronic Acid-Based Ocular Delivery Systems." Pharmaceutics 10, no. 3 (August 1, 2018): 110. http://dx.doi.org/10.3390/pharmaceutics10030110.
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Polymer-based eye drops are the most used drug delivery system to treat dry eye disease (DED). Therefore, the mucoadhesion between the polymer and the ocular mucin is crucial to ensure the efficacy of the treatment. In this context, the present study aimed to evaluate the potential use of in vitro methods to study the mucoadhesion of eye drop solutions and, specifically to evaluate the efficacy of two hyaluronic acid-based formulations (HA), HA 0.15% and 0.30% (w/v) to treat DED. Rheology methods and zeta potential determination were used to study the mucoadhesive properties of both eye drop solutions. All results indicated that interactions occurred between the mucin and the HA, being stronger with HA 0.30%, due to the physical entanglements and hydrogen bounding. In vitro tests on ARPE-19 cell line were performed using a 2D and a 3D dry eye model and the results have shown that pre-treated cells with HA showed a morphology more similar to the hydrated cells in both products, with a high survival rate. The in vitro techniques used in this study have been shown to be suitable to evaluate and predict mucoadhesive properties and the efficacy of the eye drops on relief or treatment of DED. The results obtained from these methods may help in inferring possible in vivo effects.
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Costentin, Cyril, and Jean-Michel Savéant. "Ohmic drop correction in electrochemical techniques. Multiple potential step chronoamperometry at the test bench." Energy Storage Materials 24 (January 2020): 1–3. http://dx.doi.org/10.1016/j.ensm.2019.07.029.
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SATO, Yasumoto, Takeo ATSUMI, and Tetsuo SHOJI. "Continuous Monitoring of Back-Wall Stress Corrosion Cracking Propagation by Means of Potential Drop Techniques." Transactions of the Japan Society of Mechanical Engineers Series A 72, no. 724 (2006): 1949–54. http://dx.doi.org/10.1299/kikaia.72.1949.
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Wang, Yuwei, Erqing Zhao, Liquan Fan, Qianjun Hu, Xijun Liu, Yufeng Li, and Yueping Xiong. "Analysis of nanofiber-based La0.2Sr0.8TiO3–Gd0.2Ce0.8O1.9 electrode kinetics." RSC Advances 8, no. 62 (2018): 35658–63. http://dx.doi.org/10.1039/c8ra06522e.
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Zhang, Saijun, Qinxiang Xia, Wenfang Li, and Xuhui Zhou. "Ductile damage measurement and necking analysis of metal sheets based on digital image correlation and direct current potential drop methods." International Journal of Damage Mechanics 23, no. 8 (March 19, 2014): 1133–49. http://dx.doi.org/10.1177/1056789514527978.
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In this study, a damage measurement procedure is proposed, which combines both digital image correlation and direct current potential drop techniques to evaluate quantitatively the ductile damage in metal sheets during uniaxial tensile loading. Digital image correlation and direct current potential drop techniques are applied to measure the full-field deformation and overall electrical resistance of the region of interest of the specimen during tensile loading. The basic principles, methodology and derivation process are presented in detail. A professional data processing system based on MATLAB is developed to characterize the deformation–resistance–damage relationship during uniaxial tensile loading. The ductile damage can be evaluated conveniently by the proposed approach, and the experimental results so obtained are consistent with those derived by using micro-hardness technique. The necking stage during uniaxial tension is discussed in detail, and it has been shown that the onsets of diffused necking and localized necking can be determined according to the relationship between the major principle true strain and loading steps. Further, the onset of the localized necking can be used to estimate accurately whether the material is going to rupture.
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Vičkačkaitė, Vida, and Audrius Padarauskas. "Ionic liquids in microextraction techniques." Open Chemistry 10, no. 3 (June 1, 2012): 652–74. http://dx.doi.org/10.2478/s11532-012-0023-4.
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AbstractThe tremendous potential of room temperature ionic liquids as an alternative to environmentally harmful ordinary organic solvents is well recognized. Due to their unique properties, such as low volatility, tunable viscosity and miscibility, and electrolytic conductivity, ionic liquids have attracted extensive attention and gained popularity in many areas of analytical chemistry including modern sample preparation techniques. In this review the advantages and limitations of application of ionic liquids as solvents/sorbents for microextraction are critically discussed. Topics covered include solid-phase microextraction, single drop microextraction, dispersive liquid-liquid microextraction and hollow-fiber liquid-phase microextraction. The compatibility of the ionic liquid-based microextraction with different analytical techniques such as gas chromatography, high-performance liquid chromatography, electrothermal or flame atomic absorption spectrometry and some others is also discussed. Finally, the main practical applications on this topic are summarized.
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Geldhof, Nick, Joeri Van Iseghem, Matthias Verstraete, Stijn Hertelé, Koen Van Minnebruggen, and Wim De Waele. "R-curve evaluation of pipeline girth welds using advanced measurement techniques." International Journal Sustainable Construction & Design 5, no. 1 (July 7, 2014): 10. http://dx.doi.org/10.21825/scad.v5i1.1117.
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A strain-based flaw assessment procedure is recommended for girth welded pipelines subjected to large deformations. To evaluate the allowable defect dimensions, the tearing resistance needs to be characterized. This paper investigates the effect of weld metal strength mismatch on the resistance curve using Single Edge Notched Tension (SENT) specimens. Several advanced measurement techniques are applied during the tests in order to obtain a continuous measurement of crack extension and to visualize the deformation fields near the crack. The resistance curves are determined using a single specimen technique. The unloading compliance method and the potential drop method result in similar predictions of ductile crack extension, yielding similar resistance curves. Next to these measurements, the full field deformations are determined using digital image correlation. The experiments indicate that the position of the applied notch in the weld has the potential to influence the strain fields.
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Amaral, Jorge, George Leandro Dos Santos Pinto, Gil Roberto Vieira Pinheiro, Victor Gomes Silva, and José Antônio Ponciano Gomes. "A Non-Intrusive System to Classify the Severity of Damages Caused by Internal Corrosion Using the Potential Drop Technique and Electrical Image Mapping." Journal of Integrated Circuits and Systems 15, no. 3 (December 7, 2020): 1–7. http://dx.doi.org/10.29292/jics.v15i3.181.
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This work presents a non-intrusive method to obtain information about damages caused by internal corrosion in a stainless-steel plate and classify them according to their severity. The Potential Drop technique provides an electric potential gradient map, which is analyzed by the application of image processing techniques, such as morphological analysis and segmentation. Some corrosion forms can be detected by this method, like cracks and pitting corrosion; the last one is discussed in this paper. Finite Element Modeling simulations were performed to get examples of defective plates (with two classes of damages) The image processing in the simulations acts as a feature extractor that feeds a binary classifier based on Logistic Regression, which accuracy was 99.24%.
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Wang, X., B. J. Williams, X. Wang, Y. Tang, Y. Huang, L. Kong, X. Yang, and P. Biswas. "Characterization of organic aerosol produced during pulverized coal combustion in a drop tube furnace." Atmospheric Chemistry and Physics Discussions 13, no. 2 (February 6, 2013): 3345–77. http://dx.doi.org/10.5194/acpd-13-3345-2013.
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Abstract. Controlled bench scale pulverized coal combustion studies were performed that demonstrate that inorganic particles play a critical role as carrier of organic species. Two commonly-used aerosol mass spectrometry techniques have been applied to characterize fine particle formation during coal combustion. It was found that the organic species in coal combustion aerosols have similar mass spectra as those from biomass combustion. Ambient measurements in Shanghai, China confirm the presence of these species in approximately 36~42% of the sampled particles. With the absence of major biomass sources in the Shanghai area, it is suggested that coal combustion may be the main source of these particles. This work indicates there is a significant potential for incorrect apportionment of coal combustion particles to biomass burning sources using widely adopted mass spectrometry techniques.
Dissertations / Theses on the topic "Potential drop techniques"
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Sposito, Giuseppe. "Advances in Potential Drop Techniques for Non-Destructive Testing." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/4373.
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In the field of Non-Destructive Testing, Potential Drop (PD) techniques have beenused for decades, especially in the petrochemical and power generation industries,for monitoring crack growth and wall thickness variations due to corrosion and/orerosion in pipes, pressure vessels and other structures. Inspection is carried out by injecting currents in the specimen to be tested andmeasuring the arising electrical potential di erence between two or more electrodesplaced on its surface. The presence of a defect generally increases the resistance andhence the measured voltage drop; inversion of these data can give information onthe size and shape of the defect. However, while the principle underlying these techniques is relatively simple, somedi culties have been encountered in their practical applications. Many commercialsystems based on PD methods, for instance, require the injection of very largecurrents in order to obtain su ciently large signals; doubts have been raised onthe stability of these methods to variations in the contact resistance between theelectrodes and the inspected material. The present work aims to show that someof these problems can be easily overcome, and to evaluate the capabilities of PDtechniques for crack sizing and corrosion mapping. After a brief review of the advantages, disadvantages and applications of the mainelectromagnetic methods for Non-Destructive Testing, an experimental setup forPotential Drop measurements which was developed for this work and which usessmall alternating currents (AC) is described. The setup is benchmarked against existingPD systems and then used to validate a model that allows AC PD simulationsto be run with a commercial Finite Element code. The results of both numericalsimulations and experimental measurements are used to investigate the possibilityof sizing defects of complex geometry by repeating the analysis at several di erentfrequencies over a broad range, and of reconstructing the depth pro le of surfacebreakingdefects without the need for assumptions on their shape. Subsequently, the accuracy to which it is possible to obtain maps of corrosion/erosion on the far surfaceof an inspected structure is discussed, and results obtained with an array probethat employs a novel arrangement of electrodes are presented. Finally, conclusionsare drawn and suggestions for further research are made.
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Šubrt, Stanislav. "Návrh přístroje pro analýzu vzniku a šíření trhlin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231511.
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The main goal of this thesis is to get an insight into a field of non-destructive testing using potential drop techniques that have nowadays become the standard not only in the fatigue and loading tests but also in the industry. These methods can serve to non-destructively and continuously measure material specimens, thickness, corrosion losses, deformations, spectroscopy and detection and analysis of crack geometry. They can help to identify materials and measure material changes over time. The second part of this thesis deals with designing the aperture for detection of cracks in steam and product piping using potential drop technique modified by Ing. Ladislav Korec, CSc. Last part deals with extensive testing, experimenting and evaluation of the aperture.
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Bright, Dominic. "Accurate characterisation of surface fatigue cracks (in steels) using the AC potential drop NDT technique." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5562.
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Includes bibliographical references.In order to maintain the desired level of safety in an industrial environment, it is important that the structural integrity of all the components and equipment being utilised by the facilty is assured. To determine the structural integrity of an engineering system precisely, not only must the depth of the flaw be established, but the crack profile and orientation must also be obtained in order to assess the extent of the crack. The present work described in this thesis discusses the development of an AC potential drop (ACPD) system as a non-destructive testing (NDT) technique for flaw detection and sizing of variously shaped and oriented surface breaking fatigue cracks. The ACPD method was reviewed to establish its viability as an NDT technique, and to understand the response of the output to fatigue cracking. The proposed system using a mains power source with a frequency of 50Hz was investigated as a means of providing a sensitive and reliable measurement device that could be employed to analyse fatigue cracks in industrial components in situ.
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Tarnowski, Keith. "Measuring crack initiation and growth in the presence of large strains using the potential drop technique." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/42986.
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Accurate laboratory measurements of crack initiation and growth are of vital importance for characterising material behaviour for use in the residual life assessment of structural components. The Potential Drop (PD) technique is one of the most common methods of performing these measurements, but such measurements are also sensitive to large inelastic strains which are often erroneously interpreted as crack growth. Despite the maturity of the PD technique, the extent of these errors is not fully understood and the most appropriate method of suppressing them is unknown. In this thesis typical errors in the measurement of crack extension due to large inelastic strains have been quantified experimentally. These errors depend on the PD configuration and in some cases the configurations recommended in the standards are susceptible to particularly large errors. Optimum configurations for common fracture specimens have been identified but despite these mitigating measures, when testing ductile materials, the errors due to strain remain large compared to other sources of error common to the PD technique. A sequentially coupled structural-electrical FE modelling approach has been developed which is capable of predicting the influence of strain on PD. This provides a powerful tool for decoupling the effects of strain from crack extension. It has been used in conjunction with experimental measurements, performed using a novel low frequency ACPD system (which behaves in a quasi-DC manner), to develop procedures for accurately measuring crack initiation and growth during fracture toughness and creep crack growth testing. It is demonstrated that some of the common methods of interpreting PD measurements during these tests are not fit for purpose. The proposed method of interpreting creep crack growth data has been used to re-validate creep crack initiation prediction models provided in the R5 assessment procedure.
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Doremus, Luc. "Etude expérimentale et modélisaton de la micro-propagation à partir d'anomalies de surface dans l'Inconel 718DA." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2014. http://www.theses.fr/2014ESMA0003/document.
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Les motoristes aéronautiques doivent répondre à de nouvelles demandes de certifications en tolérance aux dommages. Ils doivent en particulier démontrer que la présence de petites anomalies de surface, pouvant être introduites lors d’opérations de maintenance, ne mène pas à la rupture des pièces les plus critiques de leurs moteurs. Cette étude concerne la caractérisation de la nocivité d’anomalies de surface de type rayure et choc sur la tenue en fatigue du superalliage à base Nickel Inconel 718 sous sa version Direct Aged. Une campagne d’essais expérimentaux a permis d’évaluer l’influence de la contrainte maximale, de la température, du type et de la profondeur des anomalies de surface sur leur durée de vie en fatigue. Une étude expérimentale et numérique approfondie de la méthode de suivi de la différence de potentiel a conduit à une bonne maîtrise de cet outil de détection de l’amorçage et de suivi de la fissuration. Son utilisation a ainsi révélé que l’amorçage de fissure est très rapide à partir de rayures et de chocs mais que la vitesse de propagation dans les premiers stades de fissuration est ralentie. Des essais spécifiques ont alors été développés pour identifier la source physique des phénomènes observés. L’utilisation d’un traitement thermique a notamment permis de mettre en avant l’influence prédominante des contraintes résiduelles de compression générées lors de l’introduction des anomalies. Différentes méthodes expérimentales et numériques ont été testées pour les quantifier et des pistes de modélisations ont été mises en avant pour prédire de manière fiable la durée de vie en fatigue d’anomalies de surface de type rayure et chocAircraft engine manufacturers have to meet with new certification requirements in damage tolerance. In particular they have to demonstrate that the presence of small surface anomalies introduced on engine parts during maintenance operations in critical areas do not lead to failure during service life. This study was undertaken to characterize the harmfulness of scratch and dent type surface anomalies on the fatigue life of the Nickel based superalloy Direct Aged Inconel 718.The influence of maximal stress, temperature, type and depth of surface anomalies was evaluated in a large series of experiments. An experimental and numerical in-depth study of the potential drop technique led to a good control of this tool and allowed to efficiently detect crack initiation and to measure the crack propagation. Indeed, the use of this technique has revealed that the crack initiation from scratches and dents is very rapid but that the first stages of crack growth are delayed.Specific tests were then performed to identify the physical origin of the observed phenomenon. A heat treatment was used to show that the compressive residual stresses created during the introduction process of surface anomalies have a great influence on the fatigue life. Different experimental and numerical techniques were used to quantify these residual stresses and some directions were identified to establish a new model able to predict the fatigue life of scratch and dent type surface anomalies
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Cevik, Gul. "Investigation Of The Effect Of Orientation And Heat Treatment On The Stress Corrosion Cracking Susceptibility Of 7050 Aluminum Alloy." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605220/index.pdf.
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In the present work, the effect of variation in specimen orientation and heat treatment on the Stress Corrosion Cracking (SCC) susceptibility of 7050 aluminum alloy was investigated in 3,5% NaCl solution and under freely corroding conditions. For this purpose, Constant Extension Rate Tests (CERT) was performed on precracked Compact Tension (CT) specimens and the Direct Current Potential Drop technique was applied to measure the crack lengths. In addition to crack length versus time curves, the relationship between the crack growth rate and the stress intensity factor was determined. Fractographic analysis was utilized extensively to support the findings related with basic mechanisms of cracking.
The alloy was found to be in the most susceptible state in the SL orientation, in which the crack propagation direction is parallel to the rolling direction. The resistance to SCC is higher in the TS but at maximum in LT orientation where the loading direction is parallel to the rolling direction.
In the peak aging treatment, T651, alloy is susceptible to SCC in SL orientation. When the over aging treatment, T7651, is applied the resistance is increased and the two step over aging treatment, T73651, has resulted in an additional improvement in this orientation. On the other hand, the alloy showed higher resistance to SCC in TS and LT orientations in T651 condition compared to the T7651 and T73651 treatments. In these orientations, the alloy is less susceptible in T73651 condition than in T7651 treatment.
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Barbosa, José Fernando Cárdenas. "Fatigue crack propagation in AA 7050-T7451 alloy considering environment, stress ratio, rolling direction and waveform effects." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-27062017-111140/.
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Main extrinsic and intrinsic modifiers factors of crack growth rate in AA7050-T7451 were assessed in order to provide tools for aeronautical structures designers. These tools cover most necessary information to project aircraft\'s structures using the studied alloy, under damage tolerance philosophy. The experimental methodology consisted of use CT specimens, on TL and LT rolling direction to test its behavior under different conditions of stress ratio, force waveform, and the environment. The stress ratio values were 0.1 and 0.5, the force waveform used were sine and trapezoidal or Dwell under normal air laboratory conditions and salt fog 3.5%NaCl weight in order to simulate the marine environment. In Dwell tests, results were checked with the electrical potential drop technique (DCPD) in addition to the crack opening displacement (COD) method. Using the Walker coefficients, calculated on the present research, could be projected accurately the crack propagation behavior on Paris region and do fatigue life predictions using da/dN and S-N diagrams for different stress ratio values. The corrosion environment increases both crack growth rate and ΔKth due to oxides formation on the crack path that generates a crack closure effect. Dwell carrying makes decrease the crack growth rate by decreasing the slope of the Paris line on log (da/dN) versus log (ΔK) curve, instead of shifting down the line as occurs on titanium alloys. Rolling direction change from LT to TL increase the FCG rate in both threshold and Paris region, where the rate change use to be small.Os principais fatores modificadores extrínsecos e intrínsecos da taxa de propagação de trincas na liga AA7050-T7451 foram avaliados para fornecer subsídios para projetistas de estruturas aeronáuticas, com base na filosofía de tolerância ao dano. A metodologia experimental consistiu em ensaiar corpos de prova do tipo compact tension (CT) da liga nas direções de laminação TL e LT, para verificar seu comportamento sob diferentes razões de tensões, forma de onda e condição ambiente. Os valores de razão de tensão estudados foram 0,1 e 0,5, as formas de onda foram senoidal e trapezoidal ou de Dwell, em condições normais de laboratório, ao ar, e névoa salina 3,5% NaCl, em massa, para simular um ambiente marinho. No caso dos ensaios Dwell, os resultados foram conferidos pelo método de queda de potencial eléctrico (QPE), além do método de flexibilidade elástica. Usando os coeficientes de Walker calculados a partir dos resultados obtidos, pôde-se projetar com precisão o comportamento da propagação de trinca na região de Paris e prever a vida em fadiga usando os diagramas da/dN e S-N para diferentes valores da razão de tensões. O ambiente corrosivo aumenta tanto a taxa de propagação de trinca, quanto o valor de ΔKth por causa da formação de óxidos na trajetória da trinca, que geram um efeito de fechamento sobre a mesma. Quanto à forma de onda, verificou-se que o carregamento Dwell diminui a taxa de propagação de trinca, diminuindo a inclinação das curvas log (da/dN) versus log (ΔK) na região de Paris, ao invés de deslocá-la paralelamente como ocorre com ligas de titânio. A mudança da direção de laminação de LT para TL aumenta a taxa de propagação de trinca por fadiga (PTF) tanto na região de threshold, quanto na região de Paris, onde a mudança de taxa é pequena.
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Cussac, Paul. "Influence d’imperfections surfaciques sur la tenue en fatigue de composants nucléaires." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0001.
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Dans le contexte de l’industrie nucléaire, la présence éventuelle d’imperfections surfaciques pouvant être générées par des chutes ou frottements d’outils lors de la fabrication et la maintenance des composants se doit d’être justifiée vis-à-vis du phénomène de fatigue. L’objectif premier de cette étude est d’évaluer dans quelle mesure la présence d’imperfections de surface de l’ordre de quelques dixièmes de millimètre de profondeur peut impacter la durée de vie en fatigue oligocyclique. En parallèle, cette étude cherche à décrire, de manière qualitative et quantitative, l’amorçage et la propagation des fissures à partir de ces imperfections. Afin de répondre à ces objectifs, une campagne d’essais de fatigue uni-axiale, menée en contrôle de déformation totale imposée, a été mise en œuvre avec des éprouvettes cylindriques (Φ 9 mm). Les imperfections de surface ont été introduites artificiellement sur les éprouvettes à l’aide de deux dispositifs permettant l’usinage d’entailles de faibles dimensions. Afin de suivre les phases d’amorçage, de micro et de macro propagation des fissures à partir des imperfections de surface, la méthode du suivi de potentiel électrique a été principalement employée. Des actions expérimentales et numériques complémentaires ont été réalisées afin de calibrer le suivi de potentiel. Les résultats de la campagne d’essais réalisée mettent en évidence une influence significative de la présence d’imperfections sur la tenue en fatigue des éprouvettes étudiées. La mise en œuvre du suivi de potentiel électrique a permis de déterminer les cinétiques d’amorçage et de propagation à partir des entailles artificiellement introduites. L’identification d’un paramètre représentatif de la force motrice de propagation dans le contexte de plasticité généralisée associé aux essais réalisés a par ailleurs permis d’exploiter les données relatives aux cinétiques de propagation dans une optique prédictiveGiven the stringent requirements of high levels of safety in nuclear components, stakeholders of the French nuclear industry must anticipate the presence of residual surface imperfections in these components. Such imperfections could be introduced during manufacturing or maintenance operations. The incidence of surface irregularities on the fatigue strength of metallic components has tobe considered. Meanwhile, nuclear components can be loaded under low-cycle fatigue and large-scale plasticity conditions. The first objective of this work isthento assess to what extent the fatigue life of typical nuclear materials may be affected by the presence of such surface irregularities. In parallel, thisstudy aims at describing, qualitativelyand quantitatively, the crack initiation and propagation from these imperfections. In order to meet these objectives, a uni-axial fatigue test campaign, conducted under fully-reversed total axial strain control, in the air at room temperature, has been carried out on the cylindrical specimens (Φ 9 mm). Surface imperfections were artificially introduced onto the specimens. The electric potential trackingmethod has been mainly usedto monitor the crack initiation, micro and macro propagation phases from surface imperfections. Additional experimental and numerical actions have been carried out to calibrate the potential monitoring. The results of thetest campaigndemonstrate a significant influence of the presence of imperfections on the9 mm specimensfatigue strength. The useof electrical methodhas allowedto determine crackinitiation and growth ratesfrom surface imperfections. The identification of a representative parameter of the propagation driving force,in the context of generalized plasticity associated with the tests carried out,has also allowed to analysedata relating to propagation kinetics in a predictive perspective
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Fang, Huei-Lu, and 方輝爐. "On the Structural Defect Identification Using Direct Current-Potential Drop and Electro-Thermal Techniques." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/77038470673360418056.
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博士國立清華大學
動力機械工程學系
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To ensure the safety of structure and prevent it from catastrophic failure, it is highly desirable to seek a reliable non-destructive inspection (NDI) for detecting the defects in structure. There are numerous NDI methods for detecting the cracks or defects, among them direct current potential drop (dc-pd) technique is useful and has been proved effective. By applying direct current to the electrical conductive structure and investigating the variation of potential distribution disturbed by the discontinuity of the structure, the defects in the structure can be identified. Because of its robust and direct application on the electrical conductive structure, test can be done without the making of specimen or using expensive electronic equipment and techniques, and it also can be used in real time monitoring of engineering structure. Thus it is worth systematically exploring further this technique. This paper has firstly established the finite element analysis model for the electrical potential drop based on the electrical field theory. Then a factor, called “defect influence factor ”, has also been devised to identify the defects in an attempt to filter out the interferences caused by the parameters such as the quantity of current, input types and places of current supply, and the geometry of structure except for the defects. The factor is the ratio of the electrical potential drop on a defective structure to that of an identical one without defects. By depicting the contours of the defect influence factor , the defects of the structure can be clearly shown. For dealing with the multiple defects or cracks detection, the work has extended the finite element alternating method developed by Chen et al. (1994) originally for heat conduction analysis of multiple cracks to dc-pd to calculate the electrical potential distribution. Several samples with single or multiple defects (such as circular holes, square holes, and slots) and cracks were undergone the experiment. With the set of defect detection procedure and defect identification criteria, the shape, size, number and location of defects have been accurately identified by depicting the contours of the defect influence factor. Good agreement between the computed results of finite element method/ finite element alternating method and experimental data shows the merits of this technique. Although dc-pd technique has advantages, there are disadvantageous constraints in it. It will cause measuring difficulties due to point-to-point contact measuring using two probes. In addition, the internal resistance of structure results in joules heating which may in turn make damage to the structure parts after the currents flow through the electrical conductive structure for a while. In order to overcome these measuring constraints and thermal damages, finding to use infrared to implement non-contact thermal measurement, and establish electro-thermal (ET) technique for defect detection is also an important part of this work. Quite similar to the considerations taken in dc-pd technique, a factor called “temperature defect influence factor ” is devised for the detection of structural defects. The factor , defined as the ratio of temperature rise of a defected structure to that of a perfect one, has the effect of filtering out the possible interferences on the detection coming from parameters such as the quantity of current, input types and places of current and the geometry of structure except for defects. By depicting the contours of the temperature defect influence factor, the defects or cracks in the structure can be clearly identified. To verify the effectiveness of the ET technique newly developed in this work, in addition to the establishment of ET finite element analysis model, an infrared thermography is used to measure temperature distribution. Samples used for detection test include two thin quad flat packages (TQFP) with pop corn and debonding defects and one stainless plate with crack. The results from the former experiments are then compared with x-ray data. The comparison shows positive usefulness of the ET technique developed in this work. The defect identification criteria ( and ) of this work are variable according to the structural material. When extension this present technique to apply in the industrial product inspection, a vast calculation of the or and classified the variation with different material for establishing a table of crack test specification will be necessary. The detection of defects with dc-pd and ET technique all deals with through-wall defects or cracks, except that in TQFP specimen. But in reality, the structural defects are present in partial through-wall cracks caused by delamination, impurity, and oxidation and corrosion. Also taken into consideration is the coming of micro, nano level structures design of products. These all require high resolution of defect detection which lies ahead for future work.
Books on the topic "Potential drop techniques"
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Allen, Michael P., and Dominic J. Tildesley. Inhomogeneous fluids. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198803195.003.0014.
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In this chapter, the special techniques needed to simulate and calculate properties for inhomogeneous systems are presented. The estimation of surface properties, such as the interfacial tension, may be accomplished by a variety of methods, including the calculation of the stress tensor profiles, the change in the potential energy on scaling the surface area at constant volume, the observation of equilibrium capillary wave fluctuations, or direct free energy measurement by cleaving. The structure within the interface is also of interest, and ways of quantifying this are described. Practical issues such as system size, preparation of a two-phase system, and equilibration time, are discussed. Special application areas, such as liquid drops, fluid membranes, and liquid crystals, are described.
Book chapters on the topic "Potential drop techniques"
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Chen, Xiang, Randy K. Nanstad, and Mikhail A. Sokolov. "J-R Curve Determination for Disk-Shaped Compact Specimens Based on the Normalization Method and the Direct Current Potential Drop Technique." In Small Specimen Test Techniques: 6th Volume, 70–87. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2014. http://dx.doi.org/10.1520/stp157620140012.
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Troczynski, Thomas B., and Patrick S. Nicholson. "Application of The Potential Drop Technique to the Fracture Mechanics of Ceramics." In Fracture Mechanics of Ceramics, 199–211. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4615-7026-4_16.
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Tarnowski, K. M., C. M. Davies, D. W. Dean, and K. M. Nikbin. "The Influence of Plasticity on Crack Length Measurements Using the Potential Drop Technique." In Evaluation of Existing and New Sensor Technologies for Fatigue, Fracture and Mechanical Testing, 73–96. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2015. http://dx.doi.org/10.1520/stp158420140055.
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Reaz Ahmed, S., Masumi Saka, and Fumio Takeo. "DC Potential-Drop Technique for the Evaluation of 3-D Back-Wall Cracks in Steel Structures." In Advanced Nondestructive Evaluation I, 434–40. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-412-x.434.
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Livingstone, F., and I. M. Kilpatrick. "On-Line Fatigue Crack Growth Monitoring in Externally Pressurised Vessels Using the Alternating Current Potential Drop (ACPD) Technique." In Review of Progress in Quantitative Nondestructive Evaluation, 1531–39. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0979-6_79.
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Holmes, Douglas. "Drop the "e"." In Practicing E-Government, 199–231. IGI Global, 2005. http://dx.doi.org/10.4018/978-1-59140-637-2.ch010.
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This chapter was prepared originally for the 2002 Task Force of the OECD Project on the Impact of E-Government and was updated in 2004 for inclusion in the book, Practicing E-Government: A Global Perspective. The chapter addresses the risk of low public awareness and declining political interest as barriers to e-government, and considers ways governments can develop better marketing techniques to “sell” online services and the e-government concept to both groups. The term “marketing” is used loosely to mean both the presentation and promotion of actual online services to encourage people to use them, and the presentation and promotion of the theory and concept of e-government to ensure political understanding of its benefits to society. The chapter has two parts plus an initial Executive Summary that summarizes the points raised in both sections. Part A discusses demand-side issues: the lack of awareness and confusion among users and potential users of electronic services and how these issues can be addressed with various marketing techniques. While the greatest factor contributing to low take-up of electronic services continues to be poor Internet access and a lack of computer skills, the purpose of this report is not to address social exclusion issues. It is recognized that the digital divide is gradually being bridged and therefore the chapter primarily considers the person who has access to a computer but, for a variety of reasons, does not use it to access government services. Part B looks at the supply side and ways to market the concept of e-government to decision-makers — politicians and senior level bureaucrats — who are responsible for supporting and funding the development of online services and for removing remaining regulatory and legal barriers. The chapter does not address culture change within the public sector and the need to shift the mindset of government employees from traditional department-centric thinking into more customer-centric and user-friendly approaches. Overcoming employee resistance to new working methods requires more management skills than marketing skills. But marketing techniques can be used to address the risk of a backlash against e-government as declining political interest in the Internet generally and in e-government specifically coincides with the need to develop more complex and expensive electronic services and information systems. The author would like to thank Stefan Czerniawski, David Hickman, Chris Roberts, and Rod Quiney for their contributions.
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Radaković, Z., A. Sedmak, B. Lenkey, and V. Grabulov. "Determination of ductile crack initiation by magnetic emission and potential drop techniques using pre-cracked Charpy specimens." In From Charpy To Present Impact Testing, 71–78. Elsevier, 2002. http://dx.doi.org/10.1016/s1566-1369(02)80007-3.
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Dias Tavares Costa, Alexandre, Anna Caroline Campos Aguiar, Angelina Moraes Silva, and Dhelio Batista Pereira. "Point-of-Care Strategies Applied to Malaria Diagnosis." In Current Topics and Emerging Issues in Malaria Elimination. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96721.
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Rapid and specific diagnosis of malaria remains one of the main strategies to fight the disease. The diagnosis is made primarily by the simple and low-cost thick drop technique, considered the gold standard test. However, the requirement for good quality microscopes and well-trained personnel often lead to inaccurate diagnosis, especially in cases of mixed infections or low parasitemia. Although PCR-based tests can help in these situations, this technique requires large and sensitive equipments, being unsuitable for point of care (POC) settings. A myriad of POC diagnostic tests have being developed in the last years, relying on molecular methods but also on novel strategies. New platforms, miniaturization techniques, and multiplexing possibilities promise great potential to improve disease diagnostics through fast and accurate detection of cases, even at remote places. Here, we will address the main POC strategies developed for the diagnosis of malaria, highlighting their strengths and weakness as POC applications.
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Fawcett, W. Ronald. "Charge Transfer Equilibria at Interfaces." In Liquids, Solutions, and Interfaces. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195094329.003.0013.
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Processes in which charge is transferred from one phase to another at an interface make up an important class of interfacial reactions. Well-known examples are the reactions which occur at the electrodes of an electrochemical cell. These are electron transfer reactions, oxidation taking place at one electrode and reduction at the other. The early study of electrochemical cells provided valuable thermodynamic information about the redox processes occurring in them. When an electrochemical cell is a source of energy, for example, a battery, chemical energy is converted to electrical energy. When electrical energy is driven into an electrochemical cell from an external source, electrode reactions producing products of commercial interest are possible. Thus the general subject discussed here is of considerable practical importance. Another important class of interfacial charge transfer processes occurs at the membrane | solution interface. Some solute species can move into the membrane phase, whereas others cannot. When ions are involved in membrane selectivity, a potential drop is established at the interface. Ion transfer processes at membranes are extremely important in living organisms and form the basis for the functioning of the nervous system. Membranes are also involved in ion selective electrodes such as the ubiquitous pH electrode. These electrodes are often used in modern analytical techniques based on potentiometry. In the present chapter, the relationship between the electrode potential and the activity of the solution components in the cell is examined in detail. The connection between the Galvani potential difference at the electrode solution interface and the electrode potential on the standard redox scale is discussed. This leads to an examination of the extrathermodynamic assumption which allows one to define an absolute electrode potential. Ion transfer processes at the membrane | solution interface are then examined. Diffusion potentials within the membrane and the Donnan potentials at the interface are illustrated for both liquid and solid state membranes. Specific ion electrodes are described, and their various modes of sensing ion activities in an analyte solution discussed. The structure and type of membrane used are considered with respect to its selectivity to a particular ion over other ions.
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Troczynski, Tom B., and Patrick S. Nicholson. "POTENTIAL DROP TECHNIQUE FOR FOLLOWING HIGH-TEMPERATURE CRACK GROWTH IN CERAMICS." In Proceedings of the Metallurgical Society of the Canadian Institute of Mining and Metallurgy, 205–14. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-08-035764-5.50021-3.
Full textConference papers on the topic "Potential drop techniques"
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Corcoran, Joseph, Catrin Davies, Peter Nagy, and Peter Cawley. "Potential Drop Strain Sensor for Creep Monitoring." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28668.
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Creep is a high temperature damage mechanism of interest to the power industry and at present lacks a satisfactory monitoring technique. Existing material inspection techniques are extremely laborious while strain measurements rely on often infrequent off-load measurements. A quasi-DC directional potential drop technique is presented that is shown at both room temperature and at high temperature to act as a robust strain gauge. Resistivity changes that are expected to occur in high temperature environments are also discussed as a source of potential error in strain measurements.
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Singh, Yogesh P., Michael J. Presby, Kannan Manigandan, and Gregory N. Morscher. "Multi-Lead Direct Current Potential Drop (DCPD) for In-Situ Health Monitoring of Ceramic Matrix Composites." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75803.
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The method of direct current potential drop (DCPD) can be utilized as an effective, and convenient approach for in-situ damage detection, and as a non-destructive evaluation technique. We present the results from use of a multiprobe DCPD technique for in-situ damage detection in loading of a SiC/SiC composite. It is shown that in three different modes of loading (monotonic, fatigue, and cyclic load-unload), the sensing capabilities of DCPD technique compares well to the techniques of modal acoustic emission (AE) and digital image correlation (DIC). It was also found that DCPD technique provides a far earlier warning of failure under fatigue loading than the other two methods. In addition, we show that strategically placed multiple voltage leads on the specimen surface provides a promising way of qualitatively determining the crack initiation site. Therefore, the use of multiple lead DCPD method, together with other techniques, provides a viable option for sensing damage in ceramic matrix composites (CMCs) with complex geometries, and for applications at higher temperatures.
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Youyou, Wu, Chong Tse-Ven Steven, Xu Daqin, and Jens P. Tronskar. "Optimization in Testing Techniques for Fracture Resistance Evaluation in Sour Environments." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61556.
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Use of Single Edge Notch Tension (SENT) specimen geometry to determine the fracture toughness of the pipeline material in sour service environment has earlier been established in OMAE2009-79305(1). Optimization of the testing techniques has been made with use of implementation of Direct Current Potential Drop (DCPD). DCPD allows for the simultaneous monitoring of crack growth throughout the loading process and subsequently the fracture resistance J /CTOD R-curve can be obtained with just a single test specimen. In this paper the implementation of DCPD method in a wet sour environment using the single-specimen procedure is described and the results have been compared with those obtained using the multi-specimen approach and the results showed good agreement. Some other challenges encountered during the testing process are also addressed in this paper.
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Nennie, E. D., J. P. de Boer, and W. Schiferli. "Predicting the Gain From Deliquification Measures for European Wells." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24688.
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Various Dutch operators have identified a need for increased application of deliquification measures in their North Sea wells. To help meet this need a Joint Industry Project (JIP) was set up to identify knowledge and experience gained in the United States on gas well deliquification and transfer this to European wells. In the first phase of the project a broad overview of the techniques used to deliquify gas wells suffering from liquid loading was made together with a set of available guidelines predicting the range of application. Having identified potential techniques, a selection tool was developed which suggests the most suitable deliquification technique for a given well. The selection tool can predict the gains in production and ultimate recovery resulting from applying a range of techniques. The selection tool is based on Tubing Performance Curve (TPC) analysis combined with Inflow Performance Relationship (IPR) analysis; performance therefore depends on the pressure drop over the wellbore (as modelled in the TPC) and on reservoir characteristics. For each of these techniques, a model was available or developed to simplify their operating principles to a TPC. Results from this tool can aid in deciding which deliquification technique to implement, as it gives a clear overview of the production gain that can be expected for the different techniques [8].
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Schlosser, D. J., M. Johe, T. Humphreys, C. Lundberg, and J. L. McNichol. "Evolution of Completion Techniques in the Lower Shaunavon Tight Oil Play in Southwestern Saskatchewan." In SPE Hydraulic Fracturing Technology Conference. SPE, 2015. http://dx.doi.org/10.2118/spe-173368-ms.
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Abstract The Oil and Gas industry has explored and developed the Lower Shaunavon formation through vertical drilling and completion technology. In 2006, previously uneconomic oil reserves in the Lower Shaunavon were unlocked through horizontal drilling and completions technologies. This success is similar to the developments seen in many other formations within the Williston Basin and Western Canadian Sedimentary Basin including Crescent Point Energy's Viewfield Bakken play in southeast Saskatchewan. In the Lower Shaunavon play, the horizontal multistage completion era began in 2006, with horizontal divisions of four to six completion stages per well that utilized ball-drop sleeves and open-hole packers. By 2010, the stage count capabilities of ball-drop systems had increased and liners with nine to 16 stages per well were being run. With an acquisition in 2009, Crescent Point Energy began operating in the Lower Shaunavon area. The acquisition was part of the company's strategy to acquire large oil-in-place resource plays. Recognizing the importance that technology brings to these plays, Crescent Point Energy has continuously developed and implemented new technology. In 2009, realizing the success of coiled tubing fractured cemented liners in the southeast Saskatchewan Viewfield Bakken play, Crescent Point Energy trialed their first cemented liners in the Lower Shaunavon formation. At the same time, technology progressed with advancements in completion strategies that were focused on fracture fluids, fracture stages, tool development, pump rates, hydraulic horsepower, environmental impact, water management, and production. In 2013, another step change in technology saw the implementation of coiled tubing activated fracture sleeves in cemented liner completions. Based on field trials and well results in Q4 2013, Crescent Point Energy committed to a full cemented liner program in the Lower Shaunavon. This paper presents the evolution of Crescent Point Energy's Lower Shaunavon resource play of southwest Saskatchewan. The benefits of current completion techniques are: reductions in water use, increased production, competitive well costs, and retained wellbore functionality for potential re-fracture and waterflooding programs.
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Lee, Sungho, S. S. Sadhal, and Alexei Ye Rednikov. "An Analytical Model of External Streaming and Heat Transfer for a Levitated Flattened Liquid Drop." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32079.
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We present here the heat transfer and fluid flow analysis of an acoustically levitated flattened disk-shaped liquid drop. This work arises due to an interest in the non-contact measurement of the thermophysical properties of liquids. Such techniques have application to liquids in the undercooled state, i.e., the situation when a liquid stays in a fluidic state even when the temperature falls below the normal freezing point. This can happen when, for example, a liquid sample is held in a levitated state. Since such states are easily disrupted by measurement probes, non-contact methods are needed. We have employed a technique involving the use of acoustically levitated samples of the liquid. A thermal stimulus in the form of laser-heating causes thermocapillary motion with flow characteristics depending on the thermophysical properties of the liquid. In a gravity field, buoyancy is disruptive to this thermocapillary flow, masking it with the dominant natural convection. As one approach to minimizing the effects of buoyancy, the drop was flattened (by intense acoustic pressure) in the form of a horizontal disk, about 0.5 mm thick. As a result, with very little gravitational potential, with most of the buoyant flow suppressed, thermocapillary flow remained the dominant form of fluid motion within the drop. This flow field is visualizable and subsequent analysis for the inverse problem of the thermal property can be conducted. This calls for numerical calculations involving a heat transfer model for the flattened drop. With the presence of an acoustic field, the heat-transfer analysis requires information about the corresponding Biot number. In the presence of a high-frequency acoustic field, the steady streaming originates in a thin shear-wave layer, known as the Stokes layer, at a surface of the drop. The streaming develops into the main fluid, and is referred to as the outer streaming. Since the Stokes layer is asymptotically thin in comparison to the length scale of the problem, the outer streaming formally appears to be caused by an effective slip velocity at the boundary. The presence of the thin Stokes layer, and the slip condition at the interface, changes the character of the heat transfer mechanism which is inherently different from the traditional boundary layer. The current analysis consists of a detailed semi-analytical calculation of the flow field and the heat transfer characteristics of a levitated drop in the presence of an acoustic field.
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Tohmyoh, Hironori, Hironao Takeda, M. A. Salam Akanda, and Masumi Saka. "Manipulation of Thin Metallic Wires by Joule Heat Joining." In ASME 2009 InterPACK Conference collocated with the ASME 2009 Summer Heat Transfer Conference and the ASME 2009 3rd International Conference on Energy Sustainability. ASMEDC, 2009. http://dx.doi.org/10.1115/interpack2009-89122.
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Various kinds of metallic thin wires are expected to be key elements in future NEMS or MEMS due to their excellent physical properties and geometrical merits. However, it is not so easy task to manipulate thin wires for many kinds of application nowadays. We report manipulation techniques based on weld-joining on a substrate by Joule heating. The Pt thin wires with the diameter of about 625 nm were welded onto In wires as substrates. The Pt wires on the In substrate were taken for the three-point bending test and potential drop test for determining their mechanical and electrical properties. Moreover, based on the manipulation technique, by twisting the Pt thin wire around a core wire, simply-supported micro-coils on electrode chips were successfully fabricated, and their utility as electromagnetic actuators was realized.
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Van Minnebruggen, Koen, Matthias Verstraete, Rudi Denys, Philippe Thibaux, and Wim De Waele. "Determination of CTOD Resistance Curves in SENT Specimens With a Tilted Notch." In 2014 10th International Pipeline Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/ipc2014-33571.
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The Single Edge Notched Tension (SENT) specimen is a common tool for the determination of tearing resistance in pipeline steels and welds. However, it assumes pure mode I crack tip loading, which is unrepresentative for the evaluation of spiral seam weld flaws. To this purpose, the authors have performed SENT tests using specimens with a tilted notch. This paper evaluates experimental techniques to obtain the tearing resistance of such specimens. Mixed-mode crack opening displacement and ductile tearing are successfully measured using digital image correlation and direct current potential drop, respectively. The latter technique involves a calibration on the basis of a thermo-electric finite element model. Tearing resistance tends to increase with increasing notch tilt angle. Based on the limited number of tests performed, tilted notch SENT testing appears to be a promising tool for the assessment of spiral seam weld flaws.
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Hong, Seungbae, Jean-Luc Thiffeault, Luc G. Fre´chette, and Vijay Modi. "Numerical Study of Mixing in Microchannels With Patterned Zeta Potential Surfaces." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41912.
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In a recent study, an effective means of mixing a low Reynolds number pressure-driven flow in a micro-channel was reported by Stroock et al. [10] using trenches on the lower wall that form a staggered herringbone pattern. In the present work numerical results are reported that indicate enhanced mixing using a similar herringbone pattern in the context of an electro-osmotically driven flow in microchannels. Instead of trenches, all walls are flush, making microfabrication easier. The lower wall would have lithographically deposited polymer coatings that exhibit a zeta potential of a sign opposite to that at the other walls. These coatings are chosen to form a herringbone pattern. If mixing can be achieved using purely electro-osmotic flows, then it becomes easier to scale the channel dimensions to smaller values without the penalty of a dramatic increase in pressure drop. Moreover, the possibility of mixing with purely electro-osmotic flows that do not require time varying electric fields leads to a simpler system with fewer moving parts. With current micro-fabrication techniques, it is difficult to produce periodic patterned coatings on all four walls of a rectangular microchannel. For this reason, this study limits its scope to coatings applied only on the lower surface of the microchannel, with a rectangular cross-section. Numerical simulations are used in order to elucidate the dominant mechanism responsible for mixing, which is identified as the blinking-vortex [3]. The flow regime chosen to illustrate these effects is the same as that used by Stroock et al. [10], characterized by Reynolds numbers that are O(10−2) and Pe´clet numbers that are of O(105). The presence of patterned zeta potentials in a microchannel violates conditions of ideal electro-osmosis [4] and hence the flows are necessarily three-dimensional. The efficiency of mixing is quantified by examining particle tracks at several downstream sections of the microchannel and averaging their concentration over boxes of finite size to model diffusion. It is found that the standard deviation of the concentration decays exponentially, and that the rate of decay is independent of the Pe´clet number when the latter is sufficiently large, indicating that chaotically-enhanced mixing is occurring.
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Cheng, Qingwu, Harry Adams, and Metin Yetisir. "Emergency Core Cooling System Sump Strainer Fibre Bypass Testing and Measurement." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63855.
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The potential of losing post-Loss Of Coolant Accident (LOCA) recirculation capability due to debris blockage of Emergency Core Cooling (ECC) strainers resulted in early replacements of ECC strainers in most nuclear power plants. To validate the performance of ECC strainers, extensive testing representing plant conditions is required. Such testing programs include thin-bed and full debris load pressure drop tests, fibre bypass tests and chemical effects tests. Multiple testing loops and state-of-the-art analysis techniques have provided in-depth understanding of sump strainer performance and the effect of chemical precipitation on debris bed head loss. ECC strainers typically use perforated plates as filtering surfaces with 1.6 to 2.5 mm holes and 35 to 40% open area, allowing some particulates and fibres to pass through the strainer filtering surfaces. Recently, the bypassed fibrous debris has been identified as a potential safety concern due to its possible deposition in the reactor core and blocking of flow into fuel assemblies. In some cases, the amount of fibre that is specified as allowed to enter a reactor core is only 15 g per fuel assembly for pressurized water reactors. Characterization and quantification of bypassed fibre debris for nuclear power plants are needed to address regulatory requirements. Testing methodology and analysis techniques to address regulatory requirements and concerns are presented in this paper. In particular, a newly developed technique is presented to address debris bypass quantification.
Reports on the topic "Potential drop techniques"
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Amaya, Ashley. RTI International’s Address-Based Sampling Atlas: Drop points. RTI Press, December 2017. http://dx.doi.org/10.3768/rtipress.2017.op.0047.1712.
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The Computerized Delivery Sequence (CDS) file contains listings for nearly all addresses in the United States. Survey researchers use the CDS as a sampling frame from which to draw an address-based sample (ABS). More than 700,000 addresses on the CDS are marked as drop points, which are mail receptacles shared by multiple housing units (drop units). Drop points are a challenge to sample and present a potential source of error because of their "one-to-many" relationships. Several techniques have been developed to overcome this challenge, including deleting them from the frame or sampling all units at a given drop point. This paper serves as an introduction to these challenges, discusses the pros and cons to each "solution," and provides a list of best practices.