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1
Chang, L. "Tempering of martensite". Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370313.
Testo completo
2
Schaefer, Matthew David. "Microwave Tempering of Shrimp with Susceptors". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36251.
Testo completoAbstract (sommario):
Microwave tempering experiments were conducted on frozen blocks of shrimp (FSB) and the results were used to help determine if microwave tempering of FSB is an improved thawing method over the current, traditional method, water immersion. Results of the microwave tempering experiments were also used to help determine which microwave tempering method amongst those explored by this study is most effective.
Complete thawing of a FSB in a microwave oven was found to be impractical; however, using a combination of microwave tempering followed by water immersion can successfully thaw a FSB. After a microwave tempering experiment was conducted, the final stages of thawing were completed by using the traditional water immersion method. The amount of time to complete the thawing was recorded and is referred to as the additional thawing time. The amount of shrimp cooked during microwave tempering was also recorded and calculated as a percent. The additional thawing time and the percentage of shrimp cooked were used as criteria to compare microwave tempering experiments and also to compare microwave tempering experiments with the current method.
The first set of microwave tempering experiments explored the advantages of freezing a microwave susceptive material within the FSB before microwave tempering. FSBs with susceptors and FSBs without susceptors were tempered in a microwave oven. The FSBs were tempered in a 2450 MHz microwave oven at 255 W for 35 minutes and at 406 W for 22 minutes. The results showed that the addition of susceptors does improve the microwave tempering process. The percentage of cooked shrimp and the additional thawing time was less for FSBs with susceptors than for FSBs without susceptors. The susceptors seem to help distribute the microwave energy more evenly, which reduces runaway heating and in turn reduces the amount of shrimp cooked.
When compared to the current method, microwave tempering with susceptors reduced the total thawing time by 45% while microwave tempering without susceptors reduced the total thawing time by 43%. Both microwave tempering methods, with and without susceptors, are an improvement over the current method. The addition of susceptors does improve the microwave tempering process; however, the improvements are not significant enough to justify its recommendation.
The second set of microwave tempering experiments explored the advantages of pulse microwave tempering. During pulsed microwave tempering the microwave oven was set to a high power level and was turned ON for a period of time and then OFF for a period of time. The ON/OFF pattern was repeated throughout the microwave tempering process. Several pulsed tempering experiments were conducted at a microwave power level of 848 W and at a microwave power level of 993 W. The results showed that there is no significant advantage to using pulsed microwave energy during tempering as opposed to continuous, fixed microwave energy. The results showed that fixed microwave tempering is more effective than pulsed microwave tempering. The percentage of cooked shrimp was lower for fixed experiments than for pulsed experiments and the additional thawing time was slightly less for fixed experiments than for pulsed experiments.
A mathematical model was developed to help predict he temperature profiles of a FSB during microwave tempering. Experimental temperature data were collected at four locations within the FSB during microwave tempering by using four Luxtron Fluoroptic temperature probes and a Luxtron Fluoroptic thermometer. Overall, the temperatures predicted by the model were within 2 oC of the experimental temperatures. After the first 500 seconds or so of microwave tempering, the temperatures predicted by the model were consistently less than the experimental temperatures.
From this study it was determined that the most effective microwave tempering method, amongst those conducted in this study, of a 2.2 kg (5 lb) frozen block of shrimp was accomplished by setting the power output to 255 W and the microwave cooking (tempering) time to 35 minutes. As previously mentioned, the addition of susceptors does improve the process but the improvements are not significant enough to justify its recommendation. Pulse tempering is not an improved method over fixed tempering.Master of Science
3
Zemui, Simon. "Quenching and tempering hardness response of front axle steel beams : Different material properties during quenching and tempering". Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62747.
Testo completoAbstract (sommario):
The aim of this thesis was to investigate what the relation is between as-quench hardness and final surface hardness for steel beams is, depending on what tempering temperature is used. Also explain how chemistry, dimension and microstructure effects the final mechanical properties of the front axle beam. For this a review of literature concerning the effects was completed.Hardness measurement on the surface was performed on the ends of the beam (bottom and top). This hardness measurement was performed on 6 different front axle articles of the same material (41CrS4) and 2 different front axle articles of another material (40CrMo4). The relation diagram gives an estimation of what type of tempering temperature is needed to achieve the final hardness that is desired. Because the relation was done with some inconsistences it can’t be said to give a perfect answer. The relation diagrams only work for material 41CrS4 and 40CrMo4. For the core hardness test, 2 articles of 41CrS4 and one article of 40CrMo4 was measured on 5 different position on the cross-section, the beams for the respective articles were taken from quenched state and quenched+tempered. The beam dimensions have a significant effect when it comes to cooling down the part and achieve as close to uniform hardness as possible. Even though the Middle point of the I-section sample is one of the closest cores to the surface, it has a softer core compared with the other cores. While there exists hardness difference after quenching between different points in the core they even out after tempering. When comparing the core hardness with the surface hardness it can be said that the surface hardness is not as hard as the core because of decarburization. The microstructure analysis was done on 2 articles of 41CrS4 and one article of 40CrMo4. Samples from the 3 articles is taken from both the as-quenched state and quenched+tempered state. From the optical microscope it could be seen, that the surface of the beams decarbonizes leading to a higher amount of ferrite at the structure and softer surface. Because of this 15 mm into the material is harder than at-surface. Decarburization of the 41CrS4 steels made it so that what should have been a martensite and bainite dominated surface became a ferrite and bainite dominated.To decide the actual amount of retained austenite in the sample an XRD-analysis was performed. The XRD-analysis is done only for one article type of 41CrS4. From the front axle beam three samples of three different locations (bottom, middle, top) was taken for the analysis. For the theoretical calculation of the retained austenite vs the actual amount it can be said that is a very good representation of the total amount of retained austenite in the product. But the theoretical calculation deviates a bit from the actual amount at the top part of the beam.Syftet med denna avhandling var att undersöka vad relationen är mellan härdat ythårdhet och slut ythårdhet för stålbalkar är, beroende på vilken anlöpnings temperatur som används. Tar också upp hur kemi, dimension och mikrostruktur påverkar de sista mekaniska egenskaperna hos framaxel balken. För detta genomfördes en genomgång av litteraturen om effekterna.Hårdhetsmätning på ytan utfördes på balkens ändar (botten och toppen). Denna hårdhetsmätning utfördes på 6 olika främre axelartiklar av samma material (41CrS4) och 2 olika främre axelartiklar av annat material (40CrMo4). Relationsdiagrammet ger en uppskattning av vilken typ av anlöpningstemperatur som behövs för att uppnå den slutliga hårdheten som önskas. Eftersom förhållandet gjordes med vissa inkonsekvenser kan det inte sägas ge ett perfekt svar. Relationsdiagrammen fungerar endast för material 41CrS4 och 40CrMo4.För kärnhårdhetstestet mättes 2 artiklar av 41CrS4 och en artikel av 40CrMo4 i 5 olika positioner på tvärsnittet, stålen för respektive artiklar togs från härdat tillstånd och härdat + anlöpt. Dimensionerna har en signifikant effekt när det gäller att kyla ner delen och uppnå så nära enhetlig hårdhet som möjligt. Även om mittpunkten i I-sektionsprovet är en av de närmaste kärnorna till ytan, så har det en mjukare kärna jämfört med de andra kärnorna. Det finns hårdhetsskillnad efter härdning mellan de olika punkter men de jämnar ut sig efter anlöpningen. När man jämför kärnhårdheten med ythårdheten kan man säga att ythårdheten inte är så hård på grund av avkolning.Mikrostrukturanalysen gjordes på 2 artiklar av 41CrS4 och en artikel av 40CrMo4. Prover från de 3 artiklarna tas från både härdat tillstånd och härdat + anlöpt tillstånd. Från det optiska mikroskopet kunde man se att stålbalkens yta har blivit utsatt för avkolning vilket leder till en högre mängd ferrit vid strukturen och en mjukare yta. På grund av detta, så är 15 mm in i materialet hårare än vid ytan. Avkolning av 41CrS4 stål gjorde så att det som borde ha varit ett martensit och bainit dominerat yta blev istället ferrit och bainit dominerat.XRD-analysen görs endast för en artikelart av 41CrS4. Från fram axelbalken togs tre prov från tre olika platser (botten, mitten, toppen) för analysen. För att bestämma den verkliga mängden restaustenit i provet utfördes en XRD-analys. För den teoretiska beräkningen av den rest austeniten jämfört med det faktiska beloppet kan man säga det är en mycket bra representation av den totala mängden kvarhållen austenit i produkten. Men den teoretiska beräkningen avviker lite från den faktiska mängden vid stålens övre del.
4
Bhatnagar, Nayantara. "Annealing and Tempering for Sampling and Counting". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16323.
Testo completoAbstract (sommario):
The Markov Chain Monte Carlo (MCMC) method has been widely used in practice since the 1950's in areas such as biology, statistics, and physics. However, it is only in the last few decades that powerful techniques for obtaining rigorous performance guarantees with respect to the running time have been developed. Today, with only a few notable exceptions, most known algorithms for approximately uniform sampling and approximate counting rely on the MCMC method. This thesis focuses on algorithms that use MCMC combined with an algorithm from optimization called simulated annealing, for sampling and counting problems.
Annealing is a heuristic for finding the global optimum of a function over a large search space. It has recently emerged as a powerful technique used in conjunction with the MCMC method for sampling problems, for example in the estimation of the permanent and in algorithms for computing the volume of a convex body. We examine other applications of annealing to sampling problems as well as scenarios when it fails to converge in polynomial time.
We consider the problem of randomly generating 0-1 contingency tables. This is a well-studied problem in statistics, as well as the theory of random graphs, since it is also equivalent to generating a random bipartite graph with a prescribed degree sequence. Previously, the only algorithm known for all degree sequences was by reduction to approximating the permanent of a 0-1 matrix. We give a direct and more efficient combinatorial algorithm which relies on simulated annealing.
Simulated tempering is a variant of annealing used for sampling in which a temperature parameter is randomly raised or lowered during the simulation. The idea is that by extending the state space of the Markov chain to a polynomial number of progressively smoother distributions, parameterized by temperature, the chain could cross bottlenecks in the original space which cause slow mixing. We show that simulated tempering mixes torpidly for the 3-state ferromagnetic Potts model on the complete graph. Moreover, we disprove the conventional belief that tempering can slow fixed temperature algorithms by at most a polynomial in the number of temperatures and show that it can converge at a rate that is slower by at least an exponential factor.
5
Alderdice, Corey. "Tempering Steel: Reapproaching the Mythos of Superman". TopSCHOLAR®, 2006. http://digitalcommons.wku.edu/theses/438.
Testo completoAbstract (sommario):
This study seeks to answer a question posed in Superman #156 and frequently throughout the history of the DC Comics Universe: Must there be a Superman? In answering this question, this study seeks to seam together over sixty years of Superman to better understand the mythology associated with these narratives as well as their impact on American culture. In an analysis of Mark Waid's Superman: Birthright (2003), the basic forms of the origin narrative are addressed as well as how Waid reconstructs the mythos for the twenty-first century. The second chapter addresses deconstructive narratives and the issue of shifting the context of Superman. This particular portion of the study examines Mark Waid's Kingdom Come (1996), Mark Millar's Superman: Red Son (2003) and Alan Moore's Whatever Happened to the Man of Tomorrow? (1986). The goal of this unit is to see how deconstructive narratives both break and adhere to the established continuity of the mythos and well as how the shift affects the audience's appreciation for Superman.. Despite almost a century in publication, Superman somehow retains a popular and cultural familiarity more so than other fictional icons. Authors such as Waid, Millar, and Moore have constructed versions of Superman capable of making sense in the twenty-first century yet adhering to the ideas established by Jerry Siegel and Joel Shuster in the 1930's.
6
Tawn, Nicholas. "Towards optimality of the parallel tempering algorithm". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99796/.
Testo completoAbstract (sommario):
Markov Chain Monte Carlo (MCMC) techniques for sampling from complex probability distributions have become mainstream. Big data and high model complexity demand more scalable and robust algorithms. A famous problem with MCMC is making it robust to situations when the target distribution is multi-modal. In such cases the algorithm can become trapped in a subset of the state space and fail to escape during the entirety of the run of the algorithm. This non-exploration of the state space results in highly biased sample output. Simulated (ST) and Parallel (PT) Tempering algorithms are typically used to address multi-modality problems. These methods flatten out the target distribution using a temperature schedule. This allows the Markov chain to move freely around the state space and explore all regions of significant mass. This thesis explores two new ideas to improve the scalability of the PT algorithm. These are implemented in prototype algorithms, QuanTA and HAT, which are accompanied by supportive theoretical optimal scaling results. QuanTA focuses on improving transfer speed of the hot state mixing information to the target cold state. The associated scaling result for QuanTA shows that under mild conditions the QuanTA approach admits a higher order temperature spacing than the PT algorithm. HAT focuses on preserving modal weight through the temperature schedule. This is an issue that can lead to critically poor performance of the PT approach. The associated optimal scaling result is useful from a practical perspective. The result also challenges the notion that without modal weight preservation tempering schedules can be selected based on swap acceptance rates; an idea repeatedly used in the current literature. The new algorithms are prototype designs and have clear limitations. However, the impressive empirical performance of these new algorithms, together with supportive theory, illustrate their substantial improvement over existing methodology.
7
Peet, Mathew James. "Transformation and tempering of low-temperature bainite". Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609018.
Testo completo
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Gaude-Fugarolas, Daniel. "Modelling of transformations during induction hardening and tempering". Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/218539.
Testo completoAbstract (sommario):
There are many circumstances in industry where steel components are locally heated into the austenite phase field, and then quenched rapidly to produce a hardened region. Induction hardening is one such process used widely in the manufacture of automobile components, in particular to enhance the wear and contact-fatigue resistance of rubbing surfaces.
9
Zheng, Zhongrong. "Analysis of swapping and tempering Monte Carlo algorithms". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0006/NQ43460.pdf.
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10
Aydiner, Cahit Can Ustundag Ersan. "Investigation of thermal tempering in bulk metallic glasses /". Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-04192004-120604.
Testo completo
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Zhu, C. "3D Atom Probe Studies of the Tempering of Steels". Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531662.
Testo completo
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Saha, Podder Arijit. "Tempering of a mixture of bainite and retained austenite". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609405.
Testo completo
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Techaboonanek, Chanachon. "Precipitation during Tempering of Martensite in Fe-Cr-C alloys". Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103192.
Testo completoAbstract (sommario):
The martensite structure is the most important microstructure in tool steel due to its high hardness. However, a lack of ductility is the major drawback. In order to improve the ductility and still maintaining a suitable hardness a tempering process is needed. The tempering process will cause recovery and recrystallization in the matrix, and moreover carbides will precipitate. The specific carbides have different characteristics and thus the type of carbide formed during tempering is very important for the properties of the steel. The simulation software (TC-Prisma) is interesting because it can predict type, size, and amount of carbides. The present study was carried out to investigate both the microstructure, hardness evolution of martensite and precipitation which occurred in Fe-C-Cr steel with different compositions, tempered at 700oC. The experimental results were compared with simulation results. Micro-Vickers hardness test with a load of 100 g was used and the hardness value dropped 40% and 60% in low carbon alloy and high carbon alloy steels, respectively. The significant drop occurred during the first 30 seconds of tempering due to recovery of the matrix. Hardness values slightly decreased and then stabilized during continued tempering. The microstructure of martensite and the morphology of carbides at different tempering times were examined by scanning and transmission electron microscopy in order to study the precipitation of carbides from the nucleation and growth to coarsening. There are three types of carbides which precipitated in the Fe-C-Cr specimens: M7C3, cementite and M3C2 depending on the composition. Fe-0.16C-4.05Cr contained M7C3, Fe-0.95C-1.065Cr contained cementite and M3C2 and Fe-014C-0.983Cr and Fe-0.88C-4.12Cr contained M7C3 and cementite. M7C3 has a faceted shape and precipitates referentially at grain boundaries. On the other hand, cementite has an elongated shape and precipitated mainly at grain boundaries but also intragranulary. M3C2 has a rounded shape and was seen only in very small amounts, and seemed to precipitate at random sites. The trend of carbide growth in experiments is consistent with the simulations using TC-Prisma, but more work is needed to enable quantitative comparisons.
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Kusunoki, Takuya. "Quantification of the Tempering Response in Type 410 Steel Welds". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1607011624665895.
Testo completo
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Li, Yu. "Effect of aluminium and vanadium on the microstructure and properties of microalloyed steels". Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366804.
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Swoger-Ruston, John Paul. "The fifteen-cent guitar re-tempering the standard six-string guitar /". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ59201.pdf.
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Ren, Shuai Ren. "The effect of chocolate components and tempering on resistivity and viscosity". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461165982.
Testo completo
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Raghavan, Satyanarayanan. "Laser-based hybrid process for machining hardened steels". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47550.
Testo completoAbstract (sommario):
Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material.
The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish.
First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %).
Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field
induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region.
Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.
19
Harris, P. M. "Tempering the effects of water stress in sugar beet and potato crops". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385139.
Testo completo
20
Joubert, K. J. "The influence of tempering on the corrosion resistance of newly developed steels". Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21797.
Testo completoAbstract (sommario):
Bibliography: pages 105-113.This thesis deals with the effect of heat treatment on the localized corrosion resistance of the low carbon, chromium containing steels, designated 825, 102A and 122 which recently have been developed. The potentiodynamic polarization technique has been employed to determine the corrosion characteristics of the three steels. The results do not accurately reflect the effect heat treatment has on corrosion rates but scanning electron microscopy of corroded surfaces does allow a characterization. Both tempering temperature and time at temperature have a significant influence on the corrosion behaviour of chromium steels because the type, size and morphology of carbide precipitates are determined by the temperature and time of temperi ng. Localized pitting corrosion predominates for specimens tempered at temperatures below 450°C. Intergranular corrosion together with general corrosion occur after tempering at temperatures. in excess of 450°C. The resul ts of hardness tests show that secondary hardeni ng occurs after tempering between 450°C and 600°C. Secondary hardening suggests the presence of chromium carbides which deplete the surrounding matrix of chromium leaving it susceptible to active general corrosion (within the grains) and intergranular corrosion (at grain boundaries). A model showing the effect that 12% chromium, in comparison to 8% chromium, has on the corrosion resistance, is proposed. The significance of these results with regard to the application of the steels is discussed.
21
Bramhall, M. D. "The toughness of iron manganese alloys". Thesis, Sheffield Hallam University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234820.
Testo completo
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Chiu, Fon-Jen. "Thermomechanical processing of Ti-bearing HSLA steel". Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322984.
Testo completo
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Lawson, Benjamin James. "Compositional Optimization, Mechanical Properties, and Tempering Response in Type 410 Stainless Steel Welds". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557201840078564.
Testo completo
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Singh, Amarjit Kumar. "Development of Computer Aided Heat Treatment Planning System for Quenching & Tempering (CHT - q/t) and Industrial Application of CHT-bf & CHT-cf". Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-050306-224714/.
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Polito, Mary E. "Governing bodies tempering tongues, Henrician statecraft, subjects of governmentality and Shakespeare's Measure for measure". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ56259.pdf.
Testo completo
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Campbell, David Alexander. "Bayesian collocation tempering and generalized profiling for estimation of parameters from differential equation models". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103368.
Testo completoAbstract (sommario):
The widespread use of ordinary differential equation (ODE) models has long been underrepresented in the statistical literature. The most common methods for estimating parameters from ODE models are nonlinear least squares and an MCMC based method. Both of these methods depend on a likelihood involving the numerical solution to the ODE. The challenge faced by these methods is parameter spaces that are difficult to navigate, exacerbated by the wide variety of behaviours that a single ODE model can produce with respect to small changes in parameter values.In this work, two competing methods, generalized profile estimation and Bayesian collocation tempering are described. Both of these methods use a basis expansion to approximate the ODE solution in the likelihood, where the shape of the basis expansion, or data smooth, is guided by the ODE model. This approximation to the ODE, smooths out the likelihood surface, reducing restrictions on parameter movement.
Generalized Profile Estimation maximizes the profile likelihood for the ODE parameters while profiling out the basis coefficients of the data smooth. The smoothing parameter determines the balance between fitting the data and the ODE model, and consequently is used to build a parameter cascade, reducing the dimension of the estimation problem. Generalized profile estimation is described with under a constraint to ensure the smooth follows known behaviour such as monotonicity or non-negativity.
Bayesian collocation tempering, uses a sequence posterior densities with smooth approximations to the ODE solution. The level of the approximation is determined by the value of the smoothing parameter, which also determines the level of smoothness in the likelihood surface. In an algorithm similar to parallel tempering, parallel MCMC chains are run to sample from the sequence of posterior densities, while allowing ODE parameters to swap between chains. This method is introduced and tested against a variety of alternative Bayesian models, in terms of posterior variance and rate of convergence.
The performance of generalized profile estimation and Bayesian collocation tempering are tested and compared using simulated data sets from the FitzHugh-Nagumo ODE system and real data from nylon production dynamics.
27
Wei, Jianfei [Verfasser]. "Anisotropic Distortion of High Alloyed Tool Steels During Gas Quenching and Tempering / Jianfei Wei". Aachen : Shaker, 2004. http://d-nb.info/117261458X/34.
Testo completo
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Hilliker, Terry Lee. "The Marine Corps service planning process--the continual forging and tempering of the sword". Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27125.
Testo completoAbstract (sommario):
This thesis will examine, describe, and analyze the Marine Corps service planning process to determine the extent that it is strategic associated with strategic management. This will be followed by a synopsis of military structures and processes, as well as the external and internal influences which make up the ever changing backdrop for the Marine Corps service planning process. Finally, the Marine Corps service planning process, which encompasses the informal and formal processes that steer the actions, thinking, and planning efforts of the Marine Corps, will be described and analyzed to determine its strategic value and effectiveness. Theses. (SDW)
29
Hou, Ziyong. "Study of precipitation in martensitic Fe-C-Cr alloys during tempering : Experiments and modelling". Licentiate thesis, KTH, Metallografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176430.
Testo completoAbstract (sommario):
Understanding the precipitation reaction is very important since precipitation hardening is one of the most effective strengthening mechanisms in metallic alloys. In martensitic steels, a tempering heat treatment is often performed. During tempering various new phases are precipitated and the spatial and temporal evolution of these precipitates strongly influences the properties of the steel, such as strength/ductility, creep, fatigue and hot corrosion resistance. Therefore, the possibility of quantitative modelling of the precipitation process will provide many opportunities for advanced materials and process design and optimization as well as service life assessments. The Fe-C-Cr system forms the basis for tool steels and is consequently used in many applications such as e.g. metal forming operations. They are characterized by a high hardness and good toughness, even at elevated temperatures.In the present work, the as-quenched martensitic microstructures of four Fe-C-Cr alloys with varying Cr and C contents were characterized by Light Optical Microscopy (LOM) and Electron Microscopy. The effects of Cr and C on the morphology of martensite were investigated. It was found that Cr addition had a similar effect as C on the martensitic morphology and on the ratio of high-angle grain boundary (HAGB) to low-angle grain boundary (LAGB). However, the micro-hardness was unaffected by the Cr addition whilst it was strongly influenced by the C addition.In addition, a quantitative experimental characterization of the precipitates formed during tempering of the martensite was performed. The Langer-Schwartz theory combined with the Kampmann-Wagner-Numerical (KWN) method, as implemented in the software TC-PRISMA, was used to predict the precipitation of carbides after tempering in one of the model alloys: Fe-0.15C-4.0Cr (mass%). The microstructure characterization of the as-quenched material provided vital input parameters for the modelling work and a comparison was made between the modelling predictions and the experimental results. The effect of parameters such as dislocation density, grain size and interfacial energy on the precipitation of carbides was discussed.QC 20151105
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Khodahami, Maryam. "Hydrogen uptake during Carburizing and Effusion of Hydrogen at Room Temperature and during Tempering". Thesis, KTH, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166776.
Testo completoAbstract (sommario):
The carburizing atmosphere during the case hardening process contains a large proportion of hydrogen. Due to the rapid diffusion of hydrogen a high amount of hydrogen can be absorbed by the carburizing component. The amount of absorbed hydrogen is dependent on some factors such as for example the carburizing time and component dimensions. Hydrogen diffused in material can then cause hydrogen embrittlement and in some cases cause cracking under a static load. This hydrogen must therefore be removed. High amounts of hydrogen diffuse out spontaneously at room temperature. Tempering accelerates the process. The aim of this study was to experimentally measure the amount of absorbed hydrogen after case hardening and hydrogen content after storage at room temperature and also after tempering. The effect of the enriching gas in carburizing furnace on hydrogen absorption was investigated in this study. Three steel grades with different content of alloying elements were used in this investigation. Steel samples were case hardened by gas carburizing and tempering. The hydrogen content analyses included the measurement of hydrogen content before case hardening, after case hardening and after tempering using Leco-RHEN602. Based on the results in this study it was concluded that all steel grades used in this investigation absorb hydrogen during case hardening by gas carburizing. A major part of the absorbed hydrogen is then released by effusion after being stored at room temperature and during tempering. Around 50% of the absorbed hydrogen content during gas carburizing is due to the presence of the enriching gas in the carburizing atmosphere. Around 50 % of hydrogen diffuses out of the steel specimens after one day. It is likely that all of free diffusible) hydrogen has diffused out of the specimens of two steel grades after one week at room temperature or after tempering.Vid sätthärdning består den uppkolande atmosfären till stor del av vätgas och p.g.a. vätets snabba diffusion kan stora mängder av väte absorberas i komponenten. Halten av absorberade väte beror bl.a. på sätthärdningstid och komponentens dimensioner. Väte i materialet kan sedan leda till sprickbildning vid statisk belastning. Detta väte måste därför avlägsnas. En stor del av väte diffunderar ut spontant vid rumstemperatur. Vid anlöpning går processen fortare. Syftet med denna studie var att experimentellt mäta halten av väte som absorberas under sätthärdning, samt efter att metallen har lagrats i luft vid rumstemperatur. Dessutom mättes vätehalten efter anlöpning. Dessutom undersöktes effekten av ugnsatmosfärens tillsatsgas på mängden absorberad väte efter uppkolning. Tre olika höghållfasta och låg legerade stål sorter sätthärdades genom gas uppkolning. Mängden väte analyserades innan sätthärdning, efter sätthärdning, efter lagring i rumstemperatur och efter anlöpning med hjälp av Leco-RHEN602. Enligt resultaten i denna studie, absorberar alla av de tre undersökta stålsorterna väte under sätthärdning. En stor del av det absorberade vätet diffunderar ut efter att stålet har lagrats i luft vid rumstemperatur och under anlöpning. Omkring 50 % av den absorberade vätehalten under uppkolningen är på grund av reaktionen med tillsatsgasen i ugnsatmosfären. Omkring 50 % av vätet diffunderar ut ur proverna efter en dag. Möjligen all fritt (diffunderbart) väte har diffunderat ut ur proverna i två av stålsorterna efter en vecka i rumstemperatur eller efter anlöpning.
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Baragatti, Meïli. "Sélection bayésienne de variables et méthodes de type Parallel Tempering avec et sans vraisemblance". Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX22100/document.
Testo completoAbstract (sommario):
Cette thèse se décompose en deux parties. Dans un premier temps nous nous intéressons à la sélection bayésienne de variables dans un modèle probit mixte.L'objectif est de développer une méthode pour sélectionner quelques variables pertinentes parmi plusieurs dizaines de milliers tout en prenant en compte le design d'une étude, et en particulier le fait que plusieurs jeux de données soient fusionnés. Le modèle de régression probit mixte utilisé fait partie d'un modèle bayésien hiérarchique plus large et le jeu de données est considéré comme un effet aléatoire. Cette méthode est une extension de la méthode de Lee et al. (2003). La première étape consiste à spécifier le modèle ainsi que les distributions a priori, avec notamment l'utilisation de l'a priori conventionnel de Zellner (g-prior) pour le vecteur des coefficients associé aux effets fixes (Zellner, 1986). Dans une seconde étape, nous utilisons un algorithme Metropolis-within-Gibbs couplé à la grouping (ou blocking) technique de Liu (1994) afin de surmonter certaines difficultés d'échantillonnage. Ce choix a des avantages théoriques et computationnels. La méthode développée est appliquée à des jeux de données microarray sur le cancer du sein. Cependant elle a une limite : la matrice de covariance utilisée dans le g-prior doit nécessairement être inversible. Or il y a deux cas pour lesquels cette matrice est singulière : lorsque le nombre de variables sélectionnées dépasse le nombre d'observations, ou lorsque des variables sont combinaisons linéaires d'autres variables. Nous proposons donc une modification de l'a priori de Zellner en y introduisant un paramètre de type ridge, ainsi qu'une manière de choisir les hyper-paramètres associés. L'a priori obtenu est un compromis entre le g-prior classique et l'a priori supposant l'indépendance des coefficients de régression, et se rapproche d'un a priori précédemment proposé par Gupta et Ibrahim (2007).Dans une seconde partie nous développons deux nouvelles méthodes MCMC basées sur des populations de chaînes. Dans le cas de modèles complexes ayant de nombreux paramètres, mais où la vraisemblance des données peut se calculer, l'algorithme Equi-Energy Sampler (EES) introduit par Kou et al. (2006) est apparemment plus efficace que l'algorithme classique du Parallel Tempering (PT) introduit par Geyer (1991). Cependant, il est difficile d'utilisation lorsqu'il est couplé avec un échantillonneur de Gibbs, et nécessite un stockage important de valeurs. Nous proposons un algorithme combinant le PT avec le principe d'échanges entre chaînes ayant des niveaux d'énergie similaires dans le même esprit que l'EES. Cette adaptation appelée Parallel Tempering with Equi-Energy Moves (PTEEM) conserve l'idée originale qui fait la force de l'algorithme EES tout en assurant de bonnes propriétés théoriques et une utilisation facile avec un échantillonneur de Gibbs.Enfin, dans certains cas complexes l'inférence peut être difficile car le calcul de la vraisemblance des données s'avère trop coûteux, voire impossible. De nombreuses méthodes sans vraisemblance ont été développées. Par analogie avec le Parallel Tempering, nous proposons une méthode appelée ABC-Parallel Tempering, basée sur la théorie des MCMC, utilisant une population de chaînes et permettant des échanges entre ellesThis thesis is divided into two main parts. In the first part, we propose a Bayesian variable selection method for probit mixed models. The objective is to select few relevant variables among tens of thousands while taking into account the design of a study, and in particular the fact that several datasets are merged together. The probit mixed model used is considered as part of a larger hierarchical Bayesian model, and the dataset is introduced as a random effect. The proposed method extends a work of Lee et al. (2003). The first step is to specify the model and prior distributions. In particular, we use the g-prior of Zellner (1986) for the fixed regression coefficients. In a second step, we use a Metropolis-within-Gibbs algorithm combined with the grouping (or blocking) technique of Liu (1994). This choice has both theoritical and practical advantages. The method developed is applied to merged microarray datasets of patients with breast cancer. However, this method has a limit: the covariance matrix involved in the g-prior should not be singular. But there are two standard cases in which it is singular: if the number of observations is lower than the number of variables, or if some variables are linear combinations of others. In such situations we propose to modify the g-prior by introducing a ridge parameter, and a simple way to choose the associated hyper-parameters. The prior obtained is a compromise between the conditional independent case of the coefficient regressors and the automatic scaling advantage offered by the g-prior, and can be linked to the work of Gupta and Ibrahim (2007).In the second part, we develop two new population-based MCMC methods. In cases of complex models with several parameters, but whose likelihood can be computed, the Equi-Energy Sampler (EES) of Kou et al. (2006) seems to be more efficient than the Parallel Tempering (PT) algorithm introduced by Geyer (1991). However it is difficult to use in combination with a Gibbs sampler, and it necessitates increased storage. We propose an algorithm combining the PT with the principle of exchange moves between chains with same levels of energy, in the spirit of the EES. This adaptation which we are calling Parallel Tempering with Equi-Energy Move (PTEEM) keeps the original idea of the EES method while ensuring good theoretical properties and a practical use in combination with a Gibbs sampler.Then, in some complex models whose likelihood is analytically or computationally intractable, the inference can be difficult. Several likelihood-free methods (or Approximate Bayesian Computational Methods) have been developed. We propose a new algorithm, the Likelihood Free-Parallel Tempering, based on the MCMC theory and on a population of chains, by using an analogy with the Parallel Tempering algorithm
32
Ragoen, Céline. "Ultra-resistant glasses produced by chemical tempering: towards a better understanding of the Na+/K+ interdiffusion mechanisms and stress relaxation processes". Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/261169.
Testo completoAbstract (sommario):
Chemical strengthening via ion exchange is commonly used in the industry to produce ultra-thin and resistant glasses used for high-tech applications. This process results in the formation of an ion-exchanged region near the glass surface that is under significant compressive stress, which tremendously improves the mechanical strength and the scratch resistance of the glass. The aim of this thesis is to deepen our fundamental understanding of the ion-exchange mechanisms. Since the mechanical strength against brittle fracture of ion-exchanged glasses depends on the compressive stress at the surface and the depth of interdiffusion, special attention was paid to the two main parameters affecting those properties: the parent glass composition and stress relaxation processes.First, the effect of the parent glass composition on interdiffusion properties was analyzed. We focused our study on the effect of the alkali oxide:alumina ratio and the ionic potential (charge:radius) of divalent cations on the interdiffusional properties. An increase of the Al2O3 content in Na+/K+ ion-exchanged silicate glasses leads to a reduction of the depth of interdiffusion layer and an enhancement of the surface compressive stress. These trends are shown to be consistent with the compositional variation of the glass connectivity and hence, the stress relaxation occurring during the ion-exchange. It is also found that the depth of interdiffusion is higher for glasses containing divalent cations with a higher ionic potential such as Mg and Zn. This is attributed to the larger free volume available and the weaker Na-O bonds in those glasses. Second, the structural origin of stress relaxation is investigated. In the Na+/K+ ion exchanged glasses, the K+-foreign cations are introduced in the cages of the Na+-host cations. Due to stress relaxation, the size of the K-O coordination shell in ion-exchanged glasses increases. This increase is achieved by two structural adaptation mechanisms: a contraction of the Na-O, Ca-O and Mg-O coordination shell and both a shortening of the Si-NBO distances and an opening of the Q4 Si-O-Si angles. The greater knowledge developed in this thesis on the effect of parent glass composition on interdiffusion mechanisms and stress relaxation processes provides further insight into practical ways to optimize the mechanical strength of ion-exchanged glasses.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Reza, Gholi Ashkan. "Effects of tempering on corrosion properties of high nitrogen alloyed tooling steels in pyrolysis oil". Thesis, KTH, Korrosionslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40471.
Testo completoAbstract (sommario):
Nowdays biofuels are becoming a good alternative for petroleum fuels due to environmental issues like high carbon dioxide emission and increasing vehicles population, together with the high price and fast depletion of petroleum oils. This project aims to investigate the corrosive effects of wood Pyrolysis oil on a special grade of nitrogen alloyed tooling steels to be used for injector nozzles in Diesel engines, where high stress and strain encounter high acidity and corrosivity of the Pyrolysis oil and cause breakdown over short periods. Vanax 35 and Vanax 75 manufactured in Uddeholm are two types of powder metallurgy high nitrogen alloyed martensitic stainless steel with a high combination of hardness (over 56HRC), low friction properties, wear resistance, anti-galling and corrosion properties. In this work, the newly developed Vanax material together with the tool steels Elmax and AISI O1 were tempered at various temperatures from 200°Cto 500°C. The tempered steels were then exposed in pyrolysis oil at 4 different temperatures, 20°C, 70°C, 95°Cand 130°C. The materials were investigated by means of corrosion rate measurements, microscopy (LOM, SEM, confocal) and Thermo-Calc calculations. The corrosion rate measurement proved that Vanax tempered at lower ranges (200°C, 400°Cand 450°C) showed the best corrosion resistance while higher tempering temperatures such as 500°C, Elmax and AISI O1 tempered at 200°Csuffered a great deal of general corrosion attack. Thermo-Calc calculations showed the formation of a hard phase, VN as primary nitrides instead of primary chromium carbides at austenizing temperature for the Vanax group. Higher amount of chromium is dissolved in solid solution in Vanax at austenizing temperature hence the martensite matrix has, after quenching, a higher chromium content that helps passivation. The loss in corrosion properties at higher tempering temperatures was due to the formation of CrN secondary phase at around 400˚C which reduces the chromium content of the martensite matrix. The results of light optical and confocal microscopy showed the presence of pits when tempering at 400˚C and 450˚C. No pits were observed at 200˚C. Elmax was not passivated at all which resulted in general corrosion attacks, due to a high chromium loss from the austenite solid solution at the austenizing procedure temperature and also the tempering temperatures. The chromium depletion from the austenite can be explained by a high carbon and a low nitrogen content in the composition which resulted in formation of a high amount of Cr7C3.
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RIBEIRO, LUIS PAULO PIRES GONCALVES. "CARACTHERIZATION OF MECHANICAL PROPERTIES ON SAE 4140 STEEL AFTER DIFFERENT TREATMENTS OF QUENCHING AND TEMPERING". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9657@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Os aços de alta resistência e baixa liga (ARBL) pertencem a uma classe de aços que desperta o interesse de pesquisadores da área metal-mecânica. A pesquisa teve como objetivos estudar a influência dos tratamentos térmicos de têmpera e revenido sobre as propriedades do aço SAE 4140 e avaliar o comportamento do aço SAE 4140 quando submetido ao revenido na faixa de temperatura característica da fragilização. Inicialmente, o material foi tratado termicamente sob diferentes condições de têmpera e revenido. Após a usinagem dos corpos de prova, foram realizados ensaios de tração e energia ao impacto, bem como caracterizações microestruturais e fractográficas. Os resultados mostraram que as propriedades mecânicas do aço SAE 4140 foram influenciadas pelos parâmetros de revenido, em particular temperatura, além do tempo de permanência no forno antes do resfriamento.
The high strength and low alloy steels (HSLA) belong to a class of steels in which researchers of the metal-mechanic area have particular interest. The aim of this work is to verify the influence of quenching and tempering heat treatments on the properties of the SAE 4140 steel as well as to evaluate its behaviour when subjected to tempering in a temperature range associated with the material´s embrittlement. At first, the material was heat treated according with different quenching and tempering conditions. In the sequence, specimens machined from the treated material were subjected to tensile and impact energy tests and characterized by microstructural and fractographic analysis. The results showed that the mechanical properties of the material were influenced by the tempering parameters, specially temperature and time of treatment as well as the permanence time of the specimens in the furnace before cooling.
35
Cezar, Henrique Musseli. "Implementação do método Parallel Tempering Monte Carlo para o estudo de propriedades termodinâmicas de nanoclusters". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-16032015-135026/.
Testo completoAbstract (sommario):
O uso de nanomateriais em aplicações como catálise e medicina, despertou nos últimos anos o interesse no estudo das propriedades de nanoclusters. O estudo das propriedades termodinâmicas desses sistemas é essencial, pois mudanças estruturais originadas de mudanças de fase podem alterar propriedades como atividade catalítica, momento magnético e propriedades óticas. A dinâmica molecular vêm sendo utilizada para o estudo computacional das propriedades termodinâmicas de diversos nanomateriais, enquanto o uso de métodos de Monte Carlo (MC), nesse contexto, tem se restringido ao estudo de nanoclusters de Lennard-Jones (LJ). Para avaliar a viabilidade do uso de métodos de MC no estudo de propriedades de sistemas reais, uma implementação do método Parallel Tempering Monte Carlo (PTMC) utilizando algoritmos do estado da arte para realização de trocas, determinação de temperaturas e ajuste de deslocamentos foi construída. Através de testes, é mostrado que alguns dos algoritmos implementados podem não ser adequados ao estudo do problema em questão. A implementação foi validada com o estudo das propriedades termodinâmicas de nanoclusters de LJ com 38, 55 e 147 átomos, que possuem resultados conhecidos na literatura. Além disso, resultados para propriedades do nanocluster LJ98 são apresentados, e devido à características estruturais desse sistema, é observada uma transição sólido-sólido entre as estruturas tetraédricas e icosaédricas em temperatura abaixo da de fusão. A hipótese do uso do algoritmo PTMC para o estudo de propriedades de materiais reais, foi testada nas nanoligas (PtCo)55 e (PtNi)55, descritas pelo potencial de Gupta. Através da comparação das estruturas de mais baixa energia com resultados de teoria do funcional da densidade (DFT, do inglês), é mostrado que o uso do potencial de Gupta pode ser justificado, dados os baixos desvios no comprimento de ligação (menores que 2.4%) e a semelhança de outras características estruturais. Os resultados obtidos indicam que o método PTMC é capaz de identificar as mudanças de fase das nanoligas estudadas. Essas mudanças são ilustradas e analisadas com o uso de um algoritmo para a comparação da similaridade de estruturas, com o qual foi possível analisar a fusão dos nanoclusters Co55, Ni55, Pt30Co25 e Pt40Ni15 (obtida em temperaturas entre 900 e 1100 K); além da fusão, a 727 K, e transição sólido-sólido, a 300 K, para a Pt55. Com as estruturas mais frequentes, encontradas através da análise de similaridade, e com a realização de cálculos DFT, foi possível observar um deslocamento do centro da banda d em direção ao HOMO (Highest Occupied Molecular Orbital) causado pelo aumento da temperatura. Esse deslocamento, segundo o modelo da banda d válido para superfícies, pode indicar uma maior reatividade dos nanoclusters nesses casos.The use of nanomaterials in applications such as catalysis and medicine, aroused in the last years interest in studying properties of nanoclusters. The study of thermodynamic properties of these systems is essential, since structural changes originated from phase changes can alter properties such as catalytic activity, magnetic moment and optical properties. Molecular dynamics have been used for the computational study of thermodynamic properties of various nanomaterials, while the use of Monte Carlo methods (MC), in this context, has been restricted to the study of Lennard-Jones (LJ) nanoclusters. To evaluate the feasibility of using MC methods to study properties of real systems, an implementation of the Parallel Tempering Monte Carlo (PTMC) method using state of the art algorithms to perform exchanges, determine the temperature set and adjust the maximum displacement, was built. Through testing, it is shown that some of the implemented algorithms may not be suitable for the study of the problem in question. The implementation was validated by studying the thermodynamic properties of LJ nanoclusters with 38, 55 and 147 atoms, which have results known in the literature. In addition, results for the properties of the LJ98 nanocluster are reported, and due to the structural features of this system, a solid-solid transition between the tetrahedral and icosahedral structures in a temperature below melting is observed. The possibility of using the PTMC algorithm in the study of properties of real materials, is tested in the (PtCo)55 and (PtNi)55 nanoalloys, described by the Gupta potential. By comparing the lowest energy structures with density functional theory (DFT) results, it is shown that the use of the Gupta potential can be justified, given the small deviation in the bond lenght (less than 2.4%) and the similarity of other structural features. The results indicate that the PTMC method is able to identify the phase changes in the studied nanoalloys. These changes are illustrated and analyzed with the use of an algorithm for comparing the structure similarity, which made possible the analysis of the melting of the Co55, Ni55, Pt30Co25 e Pt40Ni15 nanoclusters (obtained at temperatures between 900 e 1100 K); and the melting at 727 K, and solid-solid transition at 300 K, for Pt55. With the most frequent structures, obtained by the similarity analysis, and through DFT calculations, it was possible to observe a shift in the d band center to the HOMO (Highest Occupied Molecular Orbital) caused by the temperature increase. This shift, following the d band model valid for surfaces, may indicate a higher reactivity of the nanocluster in these cases.
36
Earp, Richard Wayne. "The effect of thermal tempering processes on the sharpness and injury potential of pint glasses". Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/38826.
Testo completoAbstract (sommario):
Glass drinkware is widely used in the UK. However, glasses are sometimes used as impulsive weapons in incidents related to alcohol consumption, particularly with imperial pint glasses (~568 ml). In order to reduce the potential for injury with such glasses, glass manufacturers adapted thermal tempering processes to produce tempered (also referred to as toughened) pint glasses. Tempered glass is known for its dense fracture properties and is considered to be a safer alternative to non-tempered (annealed) glass. Tempered pint glasses are now widely used throughout the UK. However, there is no standard which regulates the quality of tempered drinking glasses. This lack of standardisation has been identified as a cause for varying effectiveness of using tempered drinking glasses to reduce injury potential. This thesis aimed to examine the injury potential of pint glasses and to provide a foundation for a future standard for tempered drinking glasses. The work included: examination of the fracture properties of annealed and tempered drinking glasses; replication and analysis of physical attacks with pint glasses; and assessments into the sharpness of various glass fragments as an indicator of injury potential. The base region of tempered pint glasses was found to fracture extensively, limiting certain methods of glass attacks. Fragments from the near-rim region were found to vary significantly in size between glasses due to lower wall thicknesses and residual stress. Replications of glassing attacks indicated high forces are involved with such attacks, although the damage severity is lessened with tempered glasses. Sharpness assessments revealed little significant change in fragment sharpness due to tempering. This suggests that changes in injury potential are more likely due to practical considerations such as reduced fragment size, rather than a change in inherent sharpness properties.
37
Theron, Maritha. "Quenching and tempering effects on Rheo-cast F357 aluminium alloy during Nd: YAG laser welding". Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/26148.
Testo completoAbstract (sommario):
Al-Si-Mg casting alloys are being used in automotive applications, aerospace applications and other applications requiring heat-treatable permanent mould castings that combine good weldability with high strength and toughness (ASM). These casting alloys are also known for their excellent castability, corrosion resistance and, in particular, .a range of mechanical properties in the heattreated condition. A357 aluminum alloy has been extensively used for semi-solid processing for more than three decades, and a large amount of components like fuel rails, engine mounts, engine brackets and suspension parts have been produced. This alloy is also included in the Statement for Work between the Council for Scientific and Industrial Research (CSIR) and Boeing Co, USA. F357, a hypo-eutectic aluminium alloy, Al-7%Si-0.6%Mg without beryllium, was processed with CSIR-Rheo technology to the Semi-Solid Metal (SSM) state and cast in plates with a 50 Ton High Pressure Die Casting machine. The castings were either left in the as-cast (F) condition or subjected to T4, T4+ or T6 heat treatments prior to laser welding. Welding of aluminium alloys poses many problems like porosity, loss of alloying elements, poor bead geometry and softening of the heat affected zone. Laser welding is however widely used in industrial production owing to the advantages such as low heat input, high welding speed and high production rate. Due to these unique advantages, the potential of autogenous Nd: Y AG laser welding as manufacturing process for this cast aluminium alloy was evaluated. A welding operating window was established and the optimum parameters were found to be a laser power of 3.8 kW at the workpiece and a welding speed of 4 m/min with a twin spot laser light configuration. These laser welding parameters were applied for the welding of the heat treated plates and resulted in very low weld joint porosity and almost no loss of alloying elements. The mechanical properties of age-hardenable Al-Si-Mg alloys are dependent on the rate at which the alloy is cooled after the solution heat treatment Because of the high cooling rate during laser welding, the possibility of producing weld seams through deep penetration laser welding, with mechanical properties matching those of the T6 temper condition, but without a post-weld solid solution heat treatment, was investigated. The quench rate after laser welding was measured and compared well with that measured after solution treatment. The resulting mechanical properties of F357 aluminium welded in the T4 condition and only artificially aged after welding (T4+ condition), compares very well with the T6 base material properties. The strengthening mechanisms obtained during laser welding and the different heat treatments were studied by means of transmission electron microscopy (TEM) and are consistent with the expected precipitation hardening processes in Al-Si-Mg alloys. The quench sensitivity of SSM F357 aluminium alloy is thus sufficiently low to obtain such an increase in strength values during laser welding, that no postweld solution heat treatment is necessary to achieve mechanical properties to the T6 performance specification.
38
Cervantes, Juan. "Tempering spatial autocorrelation in the residuals of linear and generalized models by incorporating selected eigenvectors". Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6388.
Testo completoAbstract (sommario):
In order to account for spatial correlation in residuals in regression models for areal and lattice data, different disciplines have developed distinct approaches. Bayesian spatial statistics typically has used a Gaussian conditional autoregressive (CAR) prior on random effects, while geographers utilize Moran's I statistic as a measure of spatial autocorrelation and the basis for creating spatial models. Recent work in both fields has recognized and built on a common feature of the two approaches, specifically the implicit or explicit incorporation into the linear predictor of eigenvectors of a matrix representing the spatial neighborhood structure. The inclusion of appropriate choices of these vectors effectively reduces the spatial autocorrelation found in the residuals.
We begin with extensive simulation studies to compare Bayesian CAR models, Restricted Spatial Regression (RSR), Bayesian Spatial Filtering (BSF), and Eigenvector Spatial Filtering (ESF) with respect to estimation of fixed-effect coefficients, prediction, and reduction of residual spatial autocorrelation. The latter three models incorporate the neighborhood structure of the data through the eigenvectors of a Moran operator.
We propose an alternative selection algorithm for all candidate predictors that avoids the ad hoc approach of RSR and selects on both model fit and reduction of autocorrelation in the residuals. The algorithm depends on the marginal posterior density a quantity that measures what proportion of the total variance can be explained by the measurement error. The algorithm selects candidate predictors that lead to a high probability that this quantity is large in addition to having large marginal posterior inclusion probabilities (PIP) according to model fit. Two methods were constructed. The first is based on orthogonalizing all of the candidate predictors while the second can be applied to the design matrix of candidate predictors without orthogonalization.
Our algorithm was applied to the same simulated data that compared the RSR, BSF and ESF models. Although our algorithm performs similarly to the established methods, the first of our selection methods shows an improvement in execution time. In addition, our approach is a statistically sound, fully Bayesian method.
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Crespo, Gillian da Silva. "Influência do tratamento térmico superficial realizado com laser Nd:YAG pulsado no ganho de propriedades mecânicas superficiais no aço ferramenta VP 100". Ilha Solteira, 2018. http://hdl.handle.net/11449/155978.
Testo completoAbstract (sommario):
Orientador: Vicente Afonso VentrellaResumo: Dentre os diversos aços ferramenta disponíveis atualmente, encontra-se o aço VP 100, aço ferramenta de estrutura bainítica empregado no setor de fabricação de moldes e matrizes. A literatura traz diversos estudos acerca desse aço frente à processos de usinagem. Entretanto, poucos estudos tratam do comportamento desse aço frente a utilização, direta ou indireta, de processos de soldagem. Desse modo, esse trabalho analisou a influência na estrutura e, nas propriedades mecânicas (dureza e taxa de desgaste) superficiais, do aço VP 100 quando submetido a um processo de tratamento térmico superficial. O processo de tratamento térmico superficial foi realizado através da execução de sucessivos cordões de solda, autógenos, na superfície do material, por meio de um sistema de laser de estado sólido Nd:YAG na condição pulsado. O aço VP 100 foi inicialmente investigado quanto a presença de isotropia em sua estrutura, visando excluir a direção adotada para tratamento térmico como fator influenciador nos resultados. Com uma estrutura visualmente semelhante em todas as direções e, com valores de dureza médios muito próximos entre direções, a direção adotada foi excluída como fator de influência no processo. Em seguida, realizou-se cordões de solda, autógenos, em seis condições distintas (SG, AR, N, N1, N2 e N3), analisados posteriormente através de ensaios de microdureza Vickers, para determinação da melhor condição para execução do tratamento térmico. As condições N1, N2 e N3 (todas com u... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Among the steels currently available, is steel VP 100, a tool steel used in the mold and matrix manufacturing sector. There are many research on the machining process forward in this steel. However, few studies deal with work from this steel versus a direct or indirect use of welding processes. In this way, this work analyzed the influence on the structure and, under the mechanical conditions (hardness and wear rate), of the VP 100 steel when subjected to a superficial thermal treatment process. The surface heat treatment process was performed through the execution of successive weld beads, autogenous, on the surface of the material by means of a Nd: YAG solid state laser system in pulsed condition. The VP 100 steel was first investigated for the presence of isotropy in its structure, aiming the analysis if the direction took adopted for the heat treatment as an influencing factor in the results. With a visually similar structure in all directions and, with the average hardness values very close between the directions, the adopted direction was excluded as a factor of influence in the process. In the next step, weld beads, autogenous, were produced in six different condition (SG, AR, N1, N2 and N3), posterior analyzed by means of Vickers microhardness tests to determine the best condition for heat treatment. The N1, N2 and N3 conditions (all using nitrogen gas) presented the best hardness results (superficially and in the depth range of 0.30 mm), being chosen for the executio... (Complete abstract click electronic access below)
Doutor
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Seyhun, Nadide. "Modeling Of Tempering Of Frozen Potato Puree By Microwave, Infrared Assisted Microwave And Ohmic Heating Methods". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609666/index.pdf.
Testo completoAbstract (sommario):
The main purpose of this thesis is to develop a model that can predict the temperature profile inside a frozen food sample during microwave tempering and infrared assisted microwave tempering processes. Another goal of the study is to compare the tempering time of frozen foods by using microwave, infrared assisted microwave, and ohmic heating methods. Frozen potato puree was used as the food sample for all studies.
Three different microwave power levels (30%, 40%, and 50%) were used for microwave tempering studies. Three different microwave power levels (30%, 40%, and 50%) and three different infrared power levels (10%, 20%, and 30%) were
combined for infrared assisted microwave tempering. As a control, tempering was done by keeping the sample at 4°C. The increase in microwave power level and infrared power level reduced tempering time in infrared assisted microwave tempering. For the ohmic tempering studies, three different frequencies (10 kHz, 20 kHz, and 30 kHz) and three different salt contents (0.50%, 0.75%, and 1.00%) were used. The increase in frequency of ohmic heating and salt content also decreased tempering times. Microwave tempering and infrared assisted microwave tempering of frozen foods were simulated by using finite difference method. For this purpose, the change in heat capacity and the dielectric properties of frozen potato puree with respect to time were measured. The temperature distribution inside the sample was modeled, and the predicted results were compared with experimental results. The predicted temperatures showed good agreement with the experimental data (r2 >
0.985). It was possible to decrease tempering times by about 75%, 90%, and 95% using ohmic, microwave, and infrared assisted microwave tempering methods, respectively as compared to control.
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Kohlahi-Aval, J. "The influence of tempering on the impact behaviour of steel cooled at different rates after austenising". Thesis, City University London, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382802.
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Mattes, Victor R. "Microstructure and mechanical properties of HSLA-100 steel". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242937.
Testo completoAbstract (sommario):
Thesis (M.S. in Mechanical Engineering and Mechanical Engineer)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Fox, Alan G. "December 1990." Description based on title screen as viewed on April 2. 2010. DTIC Identifier(s): Steel, Microstructure, Mechanical Properties, Copper, Quenching, Tempering, Processing, Naval Vessels, HSLA-100 Steel, Theses, Age Hardening, Modulus of Elasticity, Charpy V Notch Tests. Author(s) subject terms: HSLA-100, Mechanical Properties, Copper Precipitation, Carbide. Includes bibliographical references (p. 66-68). Also available in print.
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Carzolio, Marcos Arantes. "On a Selection of Advanced Markov Chain Monte Carlo Algorithms for Everyday Use: Weighted Particle Tempering, Practical Reversible Jump, and Extensions". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71765.
Testo completoAbstract (sommario):
We are entering an exciting era, rich in the availability of data via sources such as the Internet, satellites, particle colliders, telecommunication networks, computer simulations, and the like. The confluence of increasing computational resources, volumes of data, and variety of statistical procedures has brought us to a modern enlightenment. Within the next century, these tools will combine to reveal unforeseeable insights into the social and natural sciences. Perhaps the largest headwind we now face is our collectively slow-moving imagination. Like a car on an open road, learning is limited by its own rate. Historically, slow information dissemination and the unavailability of experimental resources limited our learning. To that point, any methodological contribution that helps in the conversion of data into knowledge will accelerate us along this open road. Furthermore, if that contribution is accessible to others, the speedup in knowledge discovery scales exponentially.
Markov chain Monte Carlo (MCMC) is a broad class of powerful algorithms, typically used for Bayesian inference. Despite their variety and versatility, these algorithms rarely become mainstream workhorses because they can be difficult to implement. The humble goal of this work is to bring to the table a few more highly versatile and robust, yet easily-tuned algorithms. Specifically, we introduce weighted particle tempering, a parallelizable MCMC procedure that is adaptable to large computational resources. We also explore and develop a highly practical implementation of reversible jump, the most generalized form of MetropolisHastings. Finally, we combine these two algorithms into reversible jump weighted particle tempering, and apply it on a model and dataset that was partially collected by the author and his collaborators, halfway around the world. It is our hope that by introducing, developing, and exhibiting these algorithms, we can make a reasonable contribution to the ever-growing body of MCMC research.Ph. D.
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Barlow, Lilian D. "The effect of austenitising and tempering parameters on the microstructure and hardness of martensitic stainless steel AISI 420". Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-11262009-182934/.
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Kasto, Nanci, Elina Sargezi e Micaela Tärnhamn. "Can commitment save companies from negative publicity? : The tempering effect of commitment and corporate response on negative publicity". Thesis, Jönköping University, JIBS, EMM (Entrepreneurship, Marketing, Management), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-7794.
Testo completoAbstract (sommario):
According to Faircloth, Capella & Alford, (2001), a brand is one of the most important assets a company can possess. A brand is what the consumers relate to when differentiating one com-pany from another and therefore plays a vital role for determining competitive advantage. How-ever, in the modern world, with the increasing technology advances, companies are losing more and more control of what is said and spread about their brands. What takes companies years to build can nowadays be destroyed in just a short amount of time. When dealing with negative publicity, a company‟s actions have a crucial role in determining the outcome of the negative publicity. The theoretical literature suggests that strong respective weak corporate response, will decide whether the consumers‟ brand attitude will be improved or wors-ened. Furthermore, it is also argued that consumers‟ commitment level can temper the effects of negative publicity in the sense that the more committed a consumer is, the more he/she will re-sist a change in brand attitude. Therefore, the purpose of this study is "to examine if consumers’ atti-tude towards a brand is changed depending on strong or weak corporate response to the negative publicity. A significant aspect is to investigate and further associate the commitment variable to the outcome of change in attitudes as a result of the negative publicity."
In order to determine the cause-and-effect relationship between corporate response and brand attitude, an experiment was conducted where corporate response was the independent variable and brand attitude was the dependent variable. Furthermore, the commitment variable was in-cluded as a covariate; an independent variable not manipulated by the experimenter but still ex-pected to affect the outcome. Three different questionnaires were created: 1) Negative publicity with weak corporate response, 2) Negative publicity with strong corporate response, and 3) Negative publicity only. The experiment was conducted on consumers in Jönköping. The results indicate that whether a company decides to reply with a strong or weak corporate re-sponse to negative publicity, it will in the end have an effect on the consumers‟ brand attitude. Furthermore, the results also reveal that a consumer‟s level of commitment reinforces the effect of corporate response on his/her attitude towards a brand. In other words, the degree of the consumers‟ commitment towards a brand can temper the effect of negative publicity, ultimately saving companies from the consequences of negative publicity.
Ett varumärke är enligt Faircloth, Capella & Alford (2001), företagets viktigaste tillgång. Varu-märket spelar en viktig roll i att avgöra ett företags konkurrensfördel, då konsumenter relaterar till ett varumärke för att kunna differentiera mellan olika företag. I takt med de ökande teknolo-giska framryckningar i den moderna världen, har företag däremot börjat förlora alltmer kontroll över det som sägs och sprids om företagets varumärke. Det som tar företag åratal att bygga upp kan numera förgöras under en kort tidsperiod. När det gäller att handskas med negativ publicitet har företagets handlingar en stor inverkan på konsekvensen av den negativa publicitet som företaget har utsatts för. Den teoretiska litteraturen föreslår att stark respektive svag företagsrespons kommer att avgöra om konsumenternas attityd gentemot varumärket kommer förbättras eller försämras. Dessutom menar man att konsumen-tens lojalitetsnivå har en dämpande effekt på negativ publicitet. Ju lojalare en konsument är, des-to mer kommer han/hon att motstå en ändring i attityd gentemot varumärket i fråga trots den negativa publiciteten. Därmed är syftet med denna uppsats att ”undersöka om konsumenters attityd gentemot ett varumärke ändras beroende på stark eller svag företagsrespons i förhållande till den negativa publici-teten. En betydelsefull aspekt är att utreda och associera den kompletterande variabeln, lojalitet, med de utfallande ändringarna i attityd till följd av negativ publicitet”. I avsikt att utröna orsak-och-verkan relationen mellan företagsrespons och varumärkesattityd, ut-fördes ett experiment där företagsrespons var den oberoende variabeln och varumärkesattityd var den beroende variabeln. Därutöver, var lojalitetsvariabeln inkluderad som en covariate, dvs. en oberoende variabel som inte var manipulerad av forskarna men som ändå förväntades påver-ka resultatet. Tre olika enkäter var utformade: 1) Negativ publicitet med svag företagsrespons, 2) Negativ publicitet med stark företagsrespons, och 3) Endast negativ publicitet. Experimentet ut-fördes på konsumenter i Jönköping. Resultaten påvisar att vare sig ett företag väljer att hantera negativ publicitet genom stark eller svag företagsrespons, kommer resultatet att ha en inverkan på konsumenternas varumärkesatti-tyd. För övrigt visar resultaten att nivån av konsumentens lojalitet gentemot ett varumärk kom-mer att förstärka effekten av företagsresponsen på kundens varumärkesattityd. Med andra ord, graden av konsumenters lojalitet mot ett varumärke kan dämpa effekten av negativ publicitet och därmed rädda företag från degeneration av varumärket till följd av negativ publicitet.
Grade: VG, (ECTS) A
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Mehrabi, H. A. "Influence of tempering and normalising on the structure and properties of low alloy and plain carbon-manganese steels". Thesis, City University London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357373.
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Shan, Shengyue. "The Optimization of the Tempering Process for a Pork Belly Product on the Basis of Physical Property Simulation". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563554049641523.
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Babu, Sailesh. "A material based approach to creating wear resistant surfaces for hot forging". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1101836555.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xxii, 185 p.; also includes graphics (some col.). Includes bibliographical references (p. 178-185).
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ZEPTER, PAULO G. "Influência da microestrutura nas propriedades mecânicas do aço ABNT 5160 em condições de carregamento monotônico e cíclico". reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11585.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-10-09T12:53:34Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:34Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Yoo, Juhyun. "Effect of enzyme application in temper water on wheat milling". Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/524.
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