Academic literature on the topic 'Gas barrier model'
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Journal articles on the topic "Gas barrier model"
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MAYDANYUK, SERGEI P. "A FULLY QUANTUM METHOD OF DETERMINATION OF PENETRABILITY AND REFLECTION COEFFICIENTS IN QUANTUM FRW MODEL WITH RADIATION." International Journal of Modern Physics D 19, no. 04 (April 2010): 395–435. http://dx.doi.org/10.1142/s0218271810016464.
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In the paper the closed Friedmann–Robertson–Walker model with quantization in the presence of the positive cosmological constant and radiation is studied. For analysis of tunneling probability for birth of an asymptotically de Sitter, inflationary universe as a function of the radiation energy, a new definition of a "free" wave propagating inside strong fields is proposed. On such a basis, tunneling boundary condition is corrected, penetrability and reflection relative to the barrier are calculated in fully quantum stationary approach. For the first time nonzero interference between the incident and reflected waves has been taken into account which turns out to play important role inside cosmological potentials and could be explained by non-locality of barriers in quantum mechanics. Inside the whole region of radiation energy the tunneling probability for the birth of the inflationary universe is found to be close to its value obtained in the semiclassical approach. The reflection from the barrier is determined for the first time (which differs essentially on 1 at the energy of radiation close to the barrier height). The proposed method could be easily generalized on the cosmological models with barriers of arbitrary shape, as demonstrated for the FRW model with included Chaplygin gas. The result is stable for variations of the studied barriers, accuracy is found to be 11–18 digits for all coefficients and energies below the barrier height.
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Wu, Haoyu, Maryam Zamanian, Boguslaw Kruczek, and Jules Thibault. "Gas Permeation Model of Mixed-Matrix Membranes with Embedded Impermeable Cuboid Nanoparticles." Membranes 10, no. 12 (December 15, 2020): 422. http://dx.doi.org/10.3390/membranes10120422.
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In the packaging industry, the barrier property of packaging materials is of paramount importance. The enhancement of barrier properties of materials can be achieved by adding impermeable nanoparticles into thin polymeric films, known as mixed-matrix membranes (MMMs). Three-dimensional numerical simulations were performed to study the barrier property of these MMMs and to estimate the effective membrane gas permeability. Results show that horizontally-aligned thin cuboid nanoparticles offer far superior barrier properties than spherical nanoparticles for an identical solid volume fraction. Maxwell’s model predicts very well the relative permeability of spherical and cubic nanoparticles over a wide range of the solid volume fraction. However, Maxwell’s model shows an increasingly poor prediction of the relative permeability of MMM as the aspect ratio of cuboid nanoparticles tends to zero or infinity. An artificial neural network (ANN) model was developed successfully to predict the relative permeability of MMMs as a function of the relative thickness and the relative projected area of the embedded nanoparticles. However, since an ANN model does not provide an explicit form of the relation of the relative permeability with the physical characteristics of the MMM, a new model based on multivariable regression analysis is introduced to represent the relative permeability in a MMM with impermeable cuboid nanoparticles. The new model possesses a simple explicit form and can predict, very well, the relative permeability over an extensive range of the solid volume fraction and aspect ratio, compared with many existing models.
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Miller, R. A. "Life Modeling of Thermal Barrier Coatings for Aircraft Gas Turbine Engines." Journal of Engineering for Gas Turbines and Power 111, no. 2 (April 1, 1989): 301–5. http://dx.doi.org/10.1115/1.3240251.
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Thermal barrier coating life models developed under the NASA Lewis Research Center’s Hot Section Technology (HOST) program are summarized. An initial laboratory model and three design-capable models are discussed. Current understanding of coating failure mechanisms is also summarized.
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Jiang, Peng, and Cheng Ye. "Recession of Environmental Barrier Coatings under High-Temperature Water Vapour Conditions: A Theoretical Model." Materials 13, no. 20 (October 10, 2020): 4494. http://dx.doi.org/10.3390/ma13204494.
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Rare-earth disilicates are the major material used on the top layer of environmental barrier coating (EBC) systems. Although rare-earth disilicates are highly resistant to water vapour, corrosion due to water vapour at high temperature is still one of the main reasons of failure of EBC systems. In this study, a corrosion model of ytterbium disilicates in water vapour at high temperature was derived, based on the gas diffusion theory. Using this theoretical model, we studied the evolution rule of the corroded area on the top layer of the EBC under gas flow at high temperature. The influence of the various parameters of the external gas on the corrosion process and the corrosion kinetics curve were also discussed. The theoretical model shows that the increase in gas temperature, gas flow velocity, water partial pressure, and total gas pressure accelerate coating corrosion. Among these factors, the influence of total gas pressure on the corrosion process is relatively weak, and the effect of the continuous increase of the gas velocity on the corrosion process is limited. The shape of the corrosion kinetics curve is either a straight or parabolic, and it was determined by a combination of external gas parameters.
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Vangpaisal, Thaveesak. "Simulation of Final Cover Systems in Mitigating Landfill Gas Migration." Applied Mechanics and Materials 587-589 (July 2014): 886–91. http://dx.doi.org/10.4028/www.scientific.net/amm.587-589.886.
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Landfill cover systems have to serve as a hydraulic barrier as well as a gas barrier. The ability of multilayered cover systems to mitigate landfill gas migration was assessed. A finite element model, SEEP/W®, was used to simulate the landfill cover system. It was found that gas advective flux through the single GCL barrier was highly dependent on the differential gas pressure across the cover system and the conditions of soils above the barrier layer. The change from wet to dry condition resulted in the increase of gas flux up to 3000 times. Gas flux variations were much lower for the case of a single CCL. The use of a geomembrane on top of a CCL or a GCL significantly increased the effectiveness of the barrier layer in mitigating gas migration, particularly in a dry climatic condition. Furthermore, the change of the cover conditions had less effect on gas flux through a composite cover system than gas flux through a single barrier cover system. For the effective control of landfill gas migration, the cover system must be maintained at the high moisture content conditions.
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Al-Abduljabbar, A. "Modeling Gas Barrier Property Improvements in Polymer-Clay Nano-Composites." Journal of Nano Research 29 (December 2014): 75–84. http://dx.doi.org/10.4028/www.scientific.net/jnanor.29.75.
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Polymer-clay nanocomposites (PCNC) offer better properties at very low volume fraction of the nanofiller compared to conventional polymer composites, thus minimizing the effect on other favored properties of the polymer. The mechanism by which clay platelets, which have thicknesses of a few nanometers in size compared with several hundred nanometers in the other two dimensions, introduce mechanical and other properties improvement can be attributed to their high efficiency in introducing a discontinuity to flows through the bulk matrix polymer material. The extent of this improvement depends on the success of intercalation or separation of the clay platelets through the bulk matrix. This paper contains a general overview of polymer-clay nanocomposites in terms of properties and processing. The improvements in gas barrier properties are discussed in detail; and a model to represent the effect of introduction of nanofillers on the permeability is proposed. The model builds on previous models to explain the improvements in the gas barrier properties due to the presence of clay nanoparticles and by assuming a proper distribution of these particles.
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Miller, R. A. "Progress Toward Life Modeling of Thermal Barrier Coatings for Aircraft Gas Turbine Engines." Journal of Engineering for Gas Turbines and Power 109, no. 4 (October 1, 1987): 448–51. http://dx.doi.org/10.1115/1.3240062.
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Progress toward developing life models for simulating the behavior of thermal barrier coatings in aircraft gas turbine engines is discussed. A preliminary laboratory model is described as are current efforts to develop engine-capable models. Current understanding into failure mechanisms is also summarized.
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Malagù, C., M. C. Carotta, G. Martinelli, M. A. Ponce, M. S. Castro, and C. M. Aldao. "Field-Assisted and Thermionic Contributions to Conductance in Thick-Films." Journal of Sensors 2009 (2009): 1–5. http://dx.doi.org/10.1155/2009/402527.
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A deep analysis of conductance in nanostructured thick films has been performed. A model for field-assisted thermionic barrier crossing is being proposed to explain the film conductivity. The model has been applied to explain the behavior of resistance in vacuum of two sets of nanostructured thick-films with grains having two well-distinct characteristic radii ( nm and nm). In the first case the grain radius is shorter than the depletion region width, a limit at which overlapping of barriers takes place, and in the second case it is longer. The behavior of resistance in the presence of dry air has been explained through the mechanism of barrier modulation through gas chemisorption.
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Wang, Hong Xun, Wei Fang Zhang, and Tian Jiao Liu. "Progress in Thermal Barrier Coatings for Gas Turbine Engines." Advanced Materials Research 941-944 (June 2014): 1625–28. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.1625.
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In recent years, the key research on thermal barrier coatings (TBCs) lies in the performance improvement of materials as well as structure and process improvement, and achieves new progresses. The difficulty is application of reliability in TBCs. Researchers are exploring that employing non-destructive testing (NDT) and life prediction model on TBCs to conduct a comprehensive and real-time detection and predict the life, so as to improve the safety of TBCs in service process.
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Černušák, Ivan, and Miroslav Urban. "Effect of electron correlation on SN2 activation barriers. Fourth-order MBPT calculations." Collection of Czechoslovak Chemical Communications 53, no. 10 (1988): 2239–49. http://dx.doi.org/10.1135/cccc19882239.
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The activation barriers for a series of model gas-phase nucleophilic displacement reactions have been calculated at the MBPT(4)/DZ + P + D level. Electron correlation significantly reduces the barrier height, in most cases by about 50%. The role of individual contributions up to the fourth order MBPT is analyzed in detail showing the vital importance of single and triple excitations.
Dissertations / Theses on the topic "Gas barrier model"
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Dufresne, Michel 1962. "Fluid model of dielectric barrier gas discharge." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34520.
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A two-fluid model of dielectric barrier gas discharge is presented in this thesis. The model predicts the physical structure of the gas discharge obtained between two electrodes, when one is covered with a dielectric material: It predicts the distribution of the electron and ion particle densities, electron energy, and electric field strength. It is a self-consistent numerical model, in which the dielectric properties of the dielectric material are included and the geometry of the electrodes is taken into account, thus coupling the charged-particle transport to the electric field.New boundary conditions are developed for the electron gas at the anode; the results indicate that the common boundary conditions frequently used in the literature give solutions with non-physical behavior. The new boundary conditions give solutions with the expected physical behavior.
The equations of the model are formulated numerically using a Galerkin finite element method and solved using the Newton iteration method. New universal matrices for the finite element method are presented which can be used to construct complex finite element matrices, by replacing integrals with matrix products, in a consistent and uniform manner independent of element shape, dimensionality, and order.
Solutions for DC, pulse-waveform and time-harmonic applied electrode voltages for geometries with and without a dielectric barrier are presented. The regulating effect of the dielectric barrier by surface charge accumulation is shown for discharge under constant applied voltage, assuming a static temperature for the electron gas, for the full self-consistent model. Also, simulations of dielectric barrier discharge with applied pulse-waveform voltages are compared with simulations of applied time-harmonic voltages. The results show very similar period-averaged electric fields, electron temperature profiles, charged particle densities, and total conduction current densities. However, a much higher period-integrated ionization rate is obtained from voltage pulse simulations, compared to time-harmonic voltage simulations. Therefore, we obtain a greater reaction rate for an equivalent conduction current, in a period-averaged sense, for a discharge driven by pulse-waveform applied voltages than with time-harmonic applied voltages. Such a difference was not observed for simulations without the dielectric barrier.
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Dufresne, Michel. "Fluid model of dielectric barrier gas discharge." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ36971.pdf.
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Bhatia, Amita, and abhatia78@yahoo com. "Experimental Study of Structure and Barrier Properties of Biodegradable Nanocomposites." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090304.143545.
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As nanocomposites provide considerable improvements in material properties, scientists and engineers are focussing on biodegradable nanocomposites having superior material properties as well as degradability. This thesis has investigated the properties of biodegradable nanocomposites of the aliphatic thermoplastic polyester, poly (lactide acid) (PLA) and the synthetic biodegradable polyester, poly (butylene succinate) (PBS). To enhance the properties of this blend, nanometer-sized clay particles, have been added to produce tertiary nanocomposite. High aspect ratio and surface area of clay provide significant improvement in structural, mechanical, thermal and barrier properties in comparison to the base polymer. In this study, a series of PLA/PBS/layered silicate nanocomposites were produced by using a simple twin-screw extruder. PLA/PBS/Cloisite 30BX nanocomposites were prepared containing 1, 3, 5, 7 and 10 wt% of C30BX clay, while PLA and PBS polymers compositions were fixed at a ratio of 80 to 20. This study also included the validation of a gas barrier model for these biodegradable nanocomposites. WAXD indicated an exfoliated structure for nanocomposites having 1 and 3 wt% of clay, while predominantly development of intercalated structures was noticed for nanocomposites higher than 5 wt% of clay. However, TEM images confirmed a mixed morphology of intercalated and exfoliated structure for nanocomposite having 1 wt% of clay, while some clusters or agglomerated tactoids were detected for nanocomposites having more than 3 wt% of clay contents. The percolation threshold region for these nanocomposites lied between 3-5 wt% of clay loadings. Liquid-like behaviour of PLA/PBS blends gradually changed to solid-like behaviour with the increase in concentration of clay. Shear viscosity for the nanocomposites decreased as shear rate increased, exhibiting shear thinning non-Newtonian behaviour. Tensile strength and Young's modulus initially increased for nanocomposites of up to 3 wt% of clay but then decreased with the introduction of more clay. At high clay content (more than 3 wt%), clay particles tend to aggregate which causes microcracks at the interface of clay-polymer by lowering the polymer-clay interaction. Percentage elongation at break did not show any improvement with the addition of clay. PLA/PBS blends were considered as immiscible with each other as two separate glass transition and melting temperatures were observed in modulated differential scanning calorimetry (MDSC) thermograms. MDSC showed that crystallinity of the nanocomposites was not much affected by the addition of clay and hence some compatibilizer is required. Thermogravimetric analysis showed that the nanocomposite containing 3 wt% of clay demonstrated highest thermal stability compared to other nanocomposites. Decrease in thermal stability was noticed above 3 wt% clay; however the initial degradation temperature of nanocomposites with 5, 7 and 10 wt% of clay was higher than that of PLA/PBS blend alone. Gas barrier property measurements were undertaken to investigate the transmission of oxygen gas and water vapours. Oxygen barrier properties showed significant improvement with these nanocomposites, while that for water vapour modest improvement was observed. By comparing the relative permeabilities obtained from the experiments and the model, it was concluded that PLA/PBS/clay nanocomposites validated the Bharadwaj model for up to 3 wt% of clay concentration.
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Clum, Craig M. "Highway traffic noise barrier overlap gap model." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177442958.
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Osei-Boakye, Kwabena. "The development of diesel particulate matter (DPM) predictive model for the Barrick (Goldstrike) Meikle Mine /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1448333.
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Thesis (M.S.)--University of Nevada, Reno, 2007."August, 2007." Includes foldout illustrations. Includes bibliographical references (leaves 79-84). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Utard, Christian. "Les oscillateurs microondes faible bruit de fond a base de mesfet gaas, tegfet gaalas et transistor bipolaire silicium : modelisation, caracterisation et comparaison." Toulouse 3, 1988. http://www.theses.fr/1988TOU30078.
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On presente une methode simplifiee de modelisation fort signal des mesfet et tegfet et transistors bipolaires. Ces trois types de transistors sont utilises dans un montage oscillateur dont les caracteristiques ont ete determines de trois facons differentes, analytique par simulation electrique temporelle et par mesures experimentales. On presente enfin une etude en bruit bf et bruit mf des transistors et des oscillateurs afin de determiner le composant le plus performant. Nous proposons trois facons de determiner le coefficient de conversion bruit bf - bruit mf, par des mesures directes; indirectes et par simulation temporelle
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Davidson, Frederick Todd. "An experimental study of film cooling, thermal barrier coatings and contaminant deposition on an internally cooled turbine airfoil model." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-05-5654.
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Approximately 10% of all energy consumed in the United States is derived from high temperature gas turbine engines. As a result, a 1% increase in engine efficiency would yield enough energy to satisfy the demands of approximately 1 million homes and savings of over $800 million in fuel costs per year. Efficiency of gas turbine engines can be improved by increasing the combustor temperature. Modern engines now operate at temperatures that far exceed the material limitations of the metals they are comprised of in the pursuit of increased thermal efficiency. Various techniques to thermally protect the turbine components are used to allow for safe operation of the engines despite the extreme environments: film cooling, internal convective cooling, and thermal barrier coatings. Historically, these thermal protection techniques have been studied separately without account for any conjugate effects. The end goal of this work is to provide a greater understanding of how the conjugate effects might alter the predictions of thermal behavior and consequently improve engine designs to pursue increased efficiency.
The primary focus of this study was to complete the first open literature, high resolution experiments of a modeled first stage turbine vane with both active film cooling and a simulated thermal barrier coating (TBC). This was accomplished by scaling the thermal behavior of a real engine component to the model vane using the matched Biot number method. Various film cooling configurations were tested on both the suction and pressure side of the model vane including: round holes, craters, traditional trenches and a novel modified trench. IR thermography and ribbon thermocouples were used to measure the surface temperature of the TBC and the temperature at the interface of the TBC and vane wall, respectively. This work found that the presence of a TBC significantly dampens the effect of altering film cooling conditions when measuring the TBC interface temperature. This work also found that in certain conditions adiabatic effectiveness does not provide an accurate assessment of how a film cooling design may perform in a real engine.
An additional focus of this work was to understand how contaminant deposition alters the cooling performance of a vane with a TBC. This work focused on quantifying the detrimental effects of active deposition by seeding the mainstream flow of the test facility with simulated molten coal ash. It was found that in most cases, except for round holes operating at relatively high blowing ratios, the performance of film cooling was negatively altered by the presence of contaminant deposition. However, the cooling performance at the interface of the TBC and vane wall actually improved with deposition due to the additional thermal resistance that was added to the exterior surface of the model vane.text
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Ozbek, Ayse Merve. "Schottky barrier GaN FET model creation and verification using TCAD for technology evaluation and design." 2008. http://www.lib.ncsu.edu/theses/available/etd-03132008-111248/unrestricted/etd.pdf.
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Zhang, Yi. "Atomistic and finite element modeling of zirconia for thermal barrier coating applications." Thesis, 2014. http://hdl.handle.net/1805/6191.
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Indiana University-Purdue University Indianapolis (IUPUI)Zirconia (ZrO2) is an important ceramic material with a broad range of applications. Due to its high melting temperature, low thermal conductivity, and high-temperature stability, zirconia based ceramics have been widely used for thermal barrier coatings (TBCs). When TBC is exposed to thermal cycling during real applications, the TBC may fail due to several mechanisms: (1) phase transformation into yttrium-rich and yttrium-depleted regions, When the yttrium-rich region produces pure zirconia domains that transform between monoclinic and tetragonal phases upon thermal cycling; and (2) cracking of the coating due to stress induced by erosion. The mechanism of erosion involves gross plastic damage within the TBC, often leading to ceramic loss and/or cracks down to the bond coat. The damage mechanisms are related to service parameters, including TBC material properties, temperature, velocity, particle size, and impact angle. The goal of this thesis is to understand the structural and mechanical properties of the thermal barrier coating material, thus increasing the service lifetime of gas turbine engines. To this end, it is critical to study the fundamental properties and potential failure mechanisms of zirconia. This thesis is focused on investigating the structural and mechanical properties of zirconia. There are mainly two parts studied in this paper, (1) ab initio calculations of thermodynamic properties of both monoclinic and tetragonal phase zirconia, and monoclinic-to-tetragonal phase transformation, and (2) image-based finite element simulation of the indentation process of yttria-stabilized zirconia. In the first part of this study, the structural properties, including lattice parameter, band structure, density of state, as well as elastic constants for both monoclinic and tetragonal zirconia have been computed. The pressure-dependent phase transition between tetragonal (t-ZrO2) and cubic zirconia (c-ZrO2) has been calculated using the density function theory (DFT) method. Phase transformation is defined by the band structure and tetragonal distortion changes. The results predict a transition from a monoclinic structure to a fluorite-type cubic structure at the pressure of 37 GPa. Thermodynamic property calculations of monoclinic zirconia (m-ZrO2) were also carried out. Temperature-dependent heat capacity, entropy, free energy, Debye temperature of monoclinic zirconia, from 0 to 1000 K, were computed, and they compared well with those reported in the literature. Moreover, the atomistic simulations correctly predicted the phase transitions of m-ZrO2 under compressive pressures ranging from 0 to 70 GPa. The phase transition pressures of monoclinic to orthorhombic I (3 GPa), orthorhombic I to orthorhombic II (8 GPa), orthorhombic II to tetragonal (37 GPa), and stable tetragonal phases (37-60 GPa) are in excellent agreement with experimental data. In the second part of this study, the mechanical response of yttria-stabilized zirconia under Rockwell superficial indentation was studied. The microstructure image based finite element method was used to validate the model using a composite cermet material. Then, the finite element model of Rockwell indentation of yttria-stabilized zirconia was developed, and the result was compared with experimental hardness data.
Books on the topic "Gas barrier model"
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D, Sheffler K., Ortiz Milton, and Lewis Research Center, eds. Thermal barrier coating life prediction model development: Phase 1, final report. Cleveland, Ohio: NASA Lewis Research Center, 1989.
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Perry, Steven F., Markus Lambertz, and Anke Schmitz. Respiratory Biology of Animals. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199238460.001.0001.
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The aim of this book is to shed light on one of the most fundamental processes of life in the various lineages of animals: respiration. It provides a certain background on the physiological side of respiration, but it clearly focuses on the morphological aspects. In general, the intention of this book is to illustrate the impressive diversity of respiratory faculties (form–function complexes) rather than serving as an encyclopaedic handbook. It takes the reader on a journey through the entire realm of animals and discusses the structures involved in gas exchange, how they work, and most importantly, how all of this may be connected on an evolutionary scale. Due to the common problem, namely oxygen uptake and carbon dioxide release, and the limited number of solutions, basically surface area, barrier thickness, and physical exchange model of the respiratory organ, it is not surprising that one finds a huge number of convergences. These include, for instance, the repeated origin of tubular tracheae among several lineages of arthropods, similar lung structures in snails and amphibians, and counter-current exchange gills in bivalves and fish. However, there are certain phylogenetic constraints evident and the respiratory faculty appears as a yet to be adequately exploited source of information for systematic considerations. The ultimate goal of this book is to stimulate further research in respiratory biology, because a huge number of questions remain to be tackled on all levels, ranging from molecular through functional to especially the evolutionary aspects.
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Barker, Richard. Bioscience - Lost in Translation? Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198737780.001.0001.
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Medical innovation as it stands today is fundamentally unsustainable. There is a widening gap between what biomedical research promises and its current impact in terms of patient benefit and health system improvement. This book highlights the global problem, analyses underlying causes, and provides powerful prescriptions for change to close the gap.It contrasts progress in biomedicine with other areas of science and technology, such as information technology, in which there are faster, more reliable returns for society from scientific advance. It questions whether society is right to expect so much from biomedicine and why we have become accustomed to such poor returns.It focuses on four specific ‘gaps in translation’ between bioscience breakthroughs and ultimate patient benefit, and explains how unhelpful mental models and differing perceptions of value, risk, and uncertainty contribute to stifling progress.Specific examples are examined, in which these bottlenecks have prevented promised progress (e.g. antibiotic-resistant infections), and others in which these barriers have been overcome, as a result of patient pressure (e.g. HIV treatment) or a sense of impending crisis (e.g. pandemic influenza).
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Hajnal, Zoltan. The Context of Local Policymaking. Edited by Donald P. Haider-Markel. Oxford University Press, 2013. http://dx.doi.org/10.1093/oxfordhb/9780199579679.013.021.
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This chapter offers a critical look at the literature on one of the core questions driving the study of local politics—namely who or what governs local democracy. I outline the different theories, summarize key empirical contributions, and highlight remaining barriers. Partly because existing studies have either focused too narrowly or have been unable to test each of the different theoretical perspectives against other in a single model, the literature has not yet provided a clear answer to this question. In the conclusion, I highlight some potentially rewarding research areas that emerge from these gaps in the literature or from recent demographic or technological transformations.
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Judge, Abigail M., and Robin M. Deutsch, eds. Overcoming Parent-Child Contact Problems. Oxford University Press, 2017. http://dx.doi.org/10.1093/med:psych/9780190235208.001.0001.
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This book focuses on family-based interventions for the continuum of parent–child problems, including affinity, alignment, justified rejection, alienation, and hybrid cases. Reintegration therapy is often recommended for families with these dynamics, but relatively limited clinical writing and virtually no program evaluation data exist to inform the selection of interventions. This book helps fill this gap. In Part I, the authors review a range of topics related to this specialized area of practice: assessment and clinical decision-making, the state of research evidence for outpatient treatment, and special clinical topics such as the management of countertransference among professional teams and the use of experiential therapies to overcome treatment resistance. Part II highlights one whole-family, psychoeducational approach to parent–child contact problems known as the Overcoming Barriers approach. Founders of this program and affiliated clinicians explicate components of this model in chapters on its therapeutic milieu; psychoeducational groups for rejected parents, favored parents, and children; and coparenting and parent–child interventions. The translation of model components to outpatient practice is also discussed, and program evaluation data are presented. Authors emphasize the evolving nature of this one approach, including areas of overlap with other family interventions, and highlight lessons learned from this innovative program.
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Khanna, Muniya S., and Tommy Chou. Electronic Communication, Telehealth, and Social Media. Edited by Thomas H. Ollendick, Susan W. White, and Bradley A. White. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780190634841.013.46.
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Explosive growth of communication technologies and increased ubiquity of Internet access in both urban and rural communities and particularly in youth have occurred. Coupled with concerns regarding limitations to traditional service provision models, researchers and practitioners are looking to affordable, acceptable technologies to expand the reach of evidence-based care and reduce barriers to intervention and unmet need in areas with few providers. This chapter describes the present literature on use of video teleconferencing, web-based programs, social media, and smartphone apps to enhance mental health intervention delivery, psychiatric assessment, and training and supervision. The strengths of the various delivery methods are discussed for providing empirically supported mental healthcare, focusing on implications related to science and practice with children and families. Outlined also are current limitations, risks, and challenges to technology-mediated services, including the significant gaps in the evidence base underlying these technologies and the legal, ethical, and safety issues that remain.
Book chapters on the topic "Gas barrier model"
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Haidn, Oskar J., Nikolaus A. Adams, Rolf Radespiel, Thomas Sattelmayer, Wolfgang Schröder, Christian Stemmer, and Bernhard Weigand. "Collaborative Research for Future Space Transportation Systems." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 1–30. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_1.
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Abstract This chapter book summarizes the major achievements of the five topical focus areas, Structural Cooling, Aft-Body Flows, Combustion Chamber, Thrust Nozzle, and Thrust-Chamber Assembly of the Collaborative Research Center (Sonderforschungsbereich) Transregio 40. Obviously, only sample highlights of each of the more than twenty individual projects can be given here and thus the interested reader is invited to read their reports which again are only a summary of the entire achievements and much more information can be found in the referenced publications. The structural cooling focus area included results from experimental as well as numerical research on transpiration cooling of thrust chamber structures as well as film cooling supersonic nozzles. The topics of the aft-body flow group reached from studies of classical flow separation to interaction of rocket plumes with nozzle structures for sub-, trans-, and supersonic conditions both experimentally and numerically. Combustion instabilities, boundary layer heat transfer, injection, mixing and combustion under real gas conditions and in particular the investigation of the impact of trans-critical conditions on propellant jet disintegration and the behavior under trans-critical conditions were the subjects dealt with in the combustion chamber focus area. The thrust nozzle group worked on thermal barrier coatings and life prediction methods, investigated cooling channel flows and paid special attention to the clarification and description of fluid-structure-interaction phenomena I nozzle flows. The main emphasis of the focal area thrust-chamber assembly was combustion and heat transfer investigated in various model combustors, on dual-bell nozzle phenomena and on the definition and design of three demonstrations for which the individual projects have contributed according to their research field.
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Johnston, Craig M. T., Brad Stennes, and G. Cornelisvan Kooten. "Modeling bilateral forest products trade." In International trade in forest products: lumber trade disputes, models and examples, 43–82. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789248234.0043.
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Abstract The focus in this chapter is on the development of mathematical programming models used to model bilateral forest products trade. Theoretical outlines are provided of a multi-region, single product trade model and of an integrated, multi-region, multi-product trade model. The objective function and constraints are described mathematically, while the analysis takes into account horizontal and vertical chains and the need to calibrate the model using observed trade flows. Data sources are discussed, and the GAMS code is provided for the uncalibrated and calibrated versions of the model. The Canada-U.S. softwood lumber dispute is the raison d'être for much applied work in modeling forest products trade, especially on Canada's side. In this chapter, we examine several spatial price equilibrium (SPE) trade models that are currently used to investigate the implications of trade barriers imposed on Canadian exports of softwood lumber to the United States. The reason we consider bilateral trade is so that we can determine the impacts of trade restrictions on various regions in North America. We begin in the next section by specifying a general but vertically integrated SPE trade model.
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Johnston, Craig M. T., Brad Stennes, and G. Cornelisvan Kooten. "Modeling bilateral forest products trade." In International trade in forest products: lumber trade disputes, models and examples, 43–82. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789248234.0004.
Full textAbstract:
Abstract The focus in this chapter is on the development of mathematical programming models used to model bilateral forest products trade. Theoretical outlines are provided of a multi-region, single product trade model and of an integrated, multi-region, multi-product trade model. The objective function and constraints are described mathematically, while the analysis takes into account horizontal and vertical chains and the need to calibrate the model using observed trade flows. Data sources are discussed, and the GAMS code is provided for the uncalibrated and calibrated versions of the model. The Canada-U.S. softwood lumber dispute is the raison d'être for much applied work in modeling forest products trade, especially on Canada's side. In this chapter, we examine several spatial price equilibrium (SPE) trade models that are currently used to investigate the implications of trade barriers imposed on Canadian exports of softwood lumber to the United States. The reason we consider bilateral trade is so that we can determine the impacts of trade restrictions on various regions in North America. We begin in the next section by specifying a general but vertically integrated SPE trade model.
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Shapiro, Ania, and Putu Duff. "Sexual and Reproductive Health and Rights Inequities Among Sex Workers Across the Life Course." In Sex Work, Health, and Human Rights, 61–77. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64171-9_4.
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AbstractAll individuals, including sex workers, are entitled to the full spectrum of sexual and reproductive health (SRH) and rights. Yet sex workers continue to bear significant SRH inequities and unmet needs for appropriate SRH services at every step along their sexual and reproductive lives. To illustrate the complex and nuanced barriers that currently impede sex workers’ access to SRH services, this chapter describes the current gaps in access to SRH services experienced by sex workers globally, drawing on in-depth interviews and focus group discussions with 171 sex workers and sex worker organisations from across ten countries. Interviews highlight the lack of tailored, comprehensive, and integrated SRH services. These gaps are driven by intersecting structural forces such as: the criminalisation of sex work, same-sex relationships, and gender non-conformance; harmful and coercive SRH policies; sex work and gender-based stigma; and logistical and practical barriers. To support the SRH needs and rights of sex workers, participants recommended improved access to comprehensive, integrated services addressing sex workers’ broader SRH needs, including family planning, abortion and pregnancy needs, SRH screening, hormone therapy, and other gender-affirming services. Crucial steps towards ensuring equitable SRH access for sex workers include addressing stigma and discrimination within healthcare settings, removal of coercive SRH policies and practices, and dedicating appropriate resources towards sex worker-led SRH models within the context of decriminalisation of sex work.
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Mahala, Pramila, Amit K. Goyal, Sumitra Singh, and Suchandan Pal. "Reducing Efficiency Droop for Si-Doped Barrier Model of GaN/InGaN Multi-quantum Well Light-Emitting Diode by Designing Electron Blocking Layer." In Lecture Notes in Electrical Engineering, 565–71. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-2553-3_55.
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Klubertanz, Georg, Michel de Combarieu, Jean Croisé, and ShuichiYamamoto. "Gas flow mechanism in an engineered barrier system." In Numerical Models in Geomechanics, 369–74. Taylor & Francis, 2004. http://dx.doi.org/10.1201/9781439833780.ch53.
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Penland, Shea, and S. Jeffress Williams. "BARRIER ISLAND EROSION CONTROL MODELS USING SEDIMENT AND VEGETATION." In Coastal Depositional Systems in the Gulf of Mexico: Quaternary Framework and Environmental Issues. SEPM Society for Sedimentary Geology, 1991. http://dx.doi.org/10.5724/gcs.91.12.0186.
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Herz, Gordon I., and Charles Gaba. "Health Systems Issues and the Underserved." In Bringing Psychotherapy to the Underserved, edited by Jeffrey Zimmerman, Jeffrey E. Barnett, and Linda F. Campbell, 3–24. Oxford University Press, 2019. http://dx.doi.org/10.1093/med-psych/9780190912727.003.0001.
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A number of factors endemic to the U.S. health system contribute to barriers to meeting the mental health needs of the underserved. Important variables include the economic barrier of continued gaps in affordable third-party coverage for care, perceived and actual costs of care, insufficient numbers of clinicians relative to the number of individuals in need of mental health services, and training and workforce gaps to meet specific needs (e.g., culture, disability, geographical) of the population. Approaches being developed to counter the limited-access problem include increasing economic support for coverage of services, expanding the workforce, incorporating ethics and cultural competence in clinical training, educating consumers about real costs of care, and developing volunteer and charitable models of service provision. Future developments to decrease health system barriers are likely to include technological advances.
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Kazdin, Alan E. "Treatment Gap." In Innovations in Psychosocial Interventions and Their Delivery, edited by Alan E. Kazdin, 51–74. Oxford University Press, 2018. http://dx.doi.org/10.1093/med-psych/9780190463281.003.0003.
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This chapter details the enormous gap between the number of individuals in need of mental health services and the number who actually receive the services. Key challenges in providing services are presented, along with the barriers that must be addressed, minimized, or neutralized if interventions are to reduce the burdens of mental illness. System barriers such as the financial cost of treatment, policy and legal regulations, and limitations in the resources to provide treatment, among other obstacles are d discussed. Attitudinal barriers are addressed including stigma associated with mental illness, mental health literacy, and others. Novel additional barriers are covered including issues surrounding case identification and the model of intervention delivery.
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Nitzan, Abraham. "Vibrational Energy Relaxation." In Chemical Dynamics in Condensed Phases. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198529798.003.0020.
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An impurity molecule located as a solute in a condensed solvent, a solid matrix or a liquid, when put in an excited vibrational state will loose its excess energy due to its interaction with the surrounding solvent molecules. Vibrational energy accumulation is a precursor to all thermal chemical reactions. Its release by vibrational relaxation following a reactive barrier crossing or optically induced reaction defines the formation of a product state. The direct observation of this process by, for example, infrared emission or more often laser induced fluorescence teaches us about its characteristic timescales and their energetic (i.e. couplings and frequencies) origin. These issues are discussed in this chapter. Before turning to our main task, which is constructing and analyzing a model for vibrational relaxation in condensed phases, we make some general observations about this process. In particular we will contrast condensed phase relaxation with its gas phase counterpart and will comment on the different relaxation pathways taken by diatomic and polyatomic molecules. First, vibrational relaxation takes place also in low density gases. Collisions involving the vibrationally excited molecule may result in transfer of the excess vibrational energy to rotational and translational degrees of freedom of the overall system. Analysis based on collision theory, with the intermolecular interaction potential as input, then leads to the cross-section for inelastic collisions in which vibrational and translational/rotational energies are exchanged. If C∗ is the concentration of vibrationally excited molecules and ρ is the overall gas density, the relaxation rate coefficient kgas is defined from the bimolecular rate law When comparing this relaxation to its condensed phase counterpart one should note a technical difference between the ways relaxation rates are defined in the two phases.
Conference papers on the topic "Gas barrier model"
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Cassidy, Kevin. "The Cumulative Risk Assessment Barrier Model." In SPE Offshore Europe Oil and Gas Conference and Exhibition. Society of Petroleum Engineers, 2011. http://dx.doi.org/10.2118/146255-ms.
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Meier, Susan Manning, David M. Nissley, Keith D. Sheffler, and Thomas A. Cruse. "Thermal Barrier Coating Life Prediction Model Development." In ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-040.
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A thermal barrier coated (TBC) turbine component design system, including an accurate TBC life prediction model, is needed to realize the full potential of available TBC engine performance and/or durability benefits. The objective of this work, which was sponsored in part by NASA under the Hot Section Technology (HOST) Program (Contract NAS3-23944), was to generate a life prediction model for electron beam - physical vapor deposited (EB-PVD) zirconia TBC. Specific results include EB-PVD zirconia mechanical and physical properties, coating adherence strength measurements, interfacial oxide growth characteristics, quantitative cyclic thermal spallation life data, and a spallation life model.
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Takeuchi, Y. R., and K. Kokini. "Thermal Fracture of Multilayer Ceramic Thermal Barrier Coatings." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-318.
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Controlled experiments and a corresponding analytical model were developed to investigate the reasons for crack initiation in multilayer ceramic thermal barrier coatings. The experiments and model determined that surface cracks form as a result of tensile stresses created following stress relaxation in the ceramic at steady state high temperatures (about 900°C-1100°C). Interface cracks generated by out of plane stresses are affected by the presence of these surface cracks and thermal transients and, possibly, edge effects.
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Chan, K., S. Cheruvu, and R. Viswanathan. "Development of a Thermal Barrier Coating Life Model." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38171.
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Thermal barrier coatings (TBCs) are widely used on the first stage turbine buckets and vanes of land-based (F and G class) gas turbine machines. These coatings normally fail by spallation due to delamination of the ceramic layer along the vicinity of the thermally grown oxide (TGO)/TBC interface. The failure processes involve several mechanisms including oxidation of the bond coat, thermomechanical fatigue, sintering, and spallation of the TBC. This paper describes the development of an analytical tool for predicting the useful life of TBCs for land-based gas turbine applications. The analytical model, called TBCLIFE, has been developed to treat bond coat oxidation, sintering and spallation of the TBC, as well as effects of coating thickness and substrate curvature on TBC spallation. In addition, a parallel experimental program has also been initiated to evaluate the durability of a plasma-sprayed TBC under isothermal and thermal cycling exposures. These results will be used to determine the kinetics of TGO scale growth and the material constants for the TBC life model. The TBC life model will be applied to predicting TBC life as a function of cycle time and the results will be presented as coating life diagrams. The utility of a coating life diagram for estimating the remaining life of TBC will be illustrated and discussed.
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Zhou, Yangfan, Shengnan Wu, Jianchun Fan, and Baoqian Dai. "A Safety-Barrier-based Risk Analysis Model for Offshore Oil and Gas Leakage Incidents." In Proceedings of the 29th European Safety and Reliability Conference (ESREL). Singapore: Research Publishing Services, 2020. http://dx.doi.org/10.3850/978-981-14-8593-0_4251-cd.
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Holländer, Christian, Werner Stamm, Oliver Lüsebrink, Harald Harders, and Lorenz Singheiser. "Deposition of Fuel Impurities Within Thermal Barrier Coatings in Gas Turbine Hot Gas Paths." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14480.
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Abstract For the reliable operation of modern gas turbines, Thermal Barrier Coatings (TBCs) need to withstand a wide range of ambient conditions resulting from impurities in inlet air or fuels. A novel deposition model has been developed that enables the prediction of deposition and transport of gaseous species originating from impurities in the gas turbine working media. The successful alignment of conditions in real engines with model results will allow to address the increasing demand for more fuel- and operational flexibility of current and future gas turbines. When analyzing deposition of detrimental hot gas constituents, previous efforts largely focus on the investigation of solid and molten deposit interaction with TBCs. Recent literature and observations in gas turbines indicate that not only liquids can penetrate porous TBCs, but the deposition from gas phase inside of pores and cracks is also an aspect of TBC degradation. To investigate this vapor deposition process, a diffusion model has been coupled with a thermodynamic equilibrium solver. The diffusion model calculates vapor transport of trace elements through pores and gaps in the TBC, where the thermodynamic equilibrium solver calculates local thermodynamic equilibria to predict whether deposition takes place. The model can calculate deposition rates within TBCs by taking into account the chemical composition of impurities in the hot gas as well as pressure, temperature profile in the TBC, and the TBC’s pore structure. Utilizing the model, a wide range of different fuel chemistries can be analyzed to draw conclusions regarding possible effects on TBC lifetime. In this work the model is applied to discuss deposition properties of calcium. In recent literature calcium has — in some cases — been reported to deposit inside of TBCs as pure anhydrite (CaSO4). An actual anhydrite finding in the TBC of a stationary gas turbine blade was reproduced applying the introduced model. The vapor deposition is shown to occur within and on top of the TBC, depending on a number of factors, such as: pressure, temperatures, calcium to silicon ratio and calcium to sulfur ratio.
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Meier, Susan Manning, and Dinesh K. Gupta. "The Evolution of Thermal Barrier Coatings in Gas Turbine Engine Applications." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-203.
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Thermal barrier coatings (TBCs) have been used for almost three decades to extend the life of combustors and augmentors and, more recently, stationary turbine components. Plasma sprayed yttria stabilized zirconia TBC currently is bill-of-material on many commercial jet engine parts. A more durable electron beam-physical vapor deposited (EB-PVD) ceramic coating recently has been developed for more demanding rotating as well as stationary turbine components. This ceramic EB-PVD is bill-of-material on turbine blades and vanes in current high thrust engine models and is being considered for newer developmental engines as well. To take maximum advantage of potential TBC benefits, the thermal effect of the TBC ceramic layer must become an integral element of the hot section component design system. To do this with acceptable reliability requires a suitable analytical life prediction model calibrated to engine experience. The latest efforts in thermal barrier coatings are directed toward correlating such models to measured engine performance.
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Ruud, James A., Robert D. Lillquist, and Dennis M. Gray. "Surface Temperature Measurement of Thermal Barrier Coatings Using Infrared Pyrometry." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-281.
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A method for measuring surface temperature of semitransparent materials was developed and used to measure temperature gradients through a yttria-stabilized zirconia thermal barrier coating (TBC) heated on the front surface with a natural gas flame. A Pt stripe was deposited on the TBC surface, and its temperature was measured using infrared pyrometry at 10.6 μm. A model was developed to determine the radiant intensity emitted from a TBC on a metal substrate with a thermal gradient. The radiant intensity from TBCs was measured as a function of thermal gradient and compared with results of the model.
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Batchu, Suresh, and S. Kishore Kumar. "Steady State Thermal Analysis of an Afterburner Liner." In ASME 2013 Gas Turbine India Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gtindia2013-3615.
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Military aero engines employ afterburner system for increasing the reheat thrust required during combat and takeoff. During reheat the gas temperature in the afterburner is of the order of 2100K.The afterburner liner has to be cooled with the available bypass air to maintain metal temperature within allowable limits. The liner has cooling rings at the rear to cool the liner with tangential film cooling. This paper discusses the methodology of afterburner liner metal temperature prediction and comparison with measured metal temperature during aero engine testing at reheat condition. All the modes of heat transfer are considered for thermal analysis, radiation due to higher level of gas temperature during reheat, conduction due to presence of low conductivity thermal barrier coating and convection due to higher gas velocities are considered. At different steady state reheat conditions metal temperature are predicted and compared with measured data during aero engine testing. The predicted skin temperatures and measured temperatures are in good agreement. Empirical correlations are used for estimating the heat loads coming on the liner and adiabatic film temperature near screech holes and cooling rings. Metal temperature and thermal loads coming onto the liner are predicted with 1D code. The estimated thermal loads are applied on 3D FE model to obtain nodal temperature distribution. The thermal Analysis is carried using ANSYS software in which thermal barrier coating is also modeled. The parameters like gas temperature, thermal barrier coating thickness, coating conductivity, and coolant mass flow distribution are considered for carrying out a sensitivity analysis of liner metal temperature.
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Tanaka, Yukihisa. "Development of Numerical Simulation Method for Gas Migration Through Highly-Compacted Bentonite Using Model of Two-Phase Flow Through Deformable Porous Media." In ASME 2010 13th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2010. http://dx.doi.org/10.1115/icem2010-40012.
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In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside of the engineered barrier by anaerobic corrosion of metals used for containers, etc. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the effect of gas pressure generation and gas migration on the engineered barrier, peripheral facilities and ground. In this study, a method for simulating gas migration through the compacted bentonite is proposed. The proposed method can analyze coupled hydrological-mechanical processes using the model of two-phase flow through deformable porous media. Validity of the proposed analytical method is examined by comparing gas migration test results with the calculated results, which revealed that the proposed method can simulate gas migration behavior through compacted bentonite with accuracy.