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Auswahl der wissenschaftlichen Literatur zum Thema „Partial phase change“
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Zeitschriftenartikel zum Thema "Partial phase change"
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GOUN, A. A., und B. YA ZEL'DOVICH. „CHANGE OF PARTIAL POLARIZATION OF A BEAM UNDER PHASE CONJUGATION“. Journal of Nonlinear Optical Physics & Materials 10, Nr. 03 (September 2001): 371–75. http://dx.doi.org/10.1142/s0218863501000711.
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Possible change of the polarization state in the process of propagation is considered theoretically. We were able to suggest a mechanism that allows for a very unusual behavior of the Stokes parameters of the beam. Specially arranged phase conjugation procedure yields the decrease of only one (e.g. ∣ζ3∣∝∣(∣Ex∣2 - ∣Ey∣2)∣) Stokes component, while the degrees of 45%- and circular polarization, ζ1 and ζ2, are not changing at all.
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Braga, Stefania, Alessandro Sanasi, Alessandro Cabrini und Guido Torelli. „Voltage-Driven Partial-RESET Multilevel Programming in Phase-Change Memories“. IEEE Transactions on Electron Devices 57, Nr. 10 (Oktober 2010): 2556–63. http://dx.doi.org/10.1109/ted.2010.2062185.
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Zastawna-Rumin, Anna, Tomasz Kisilewicz und Umberto Berardi. „Novel Simulation Algorithm for Modeling the Hysteresis of Phase Change Materials“. Energies 13, Nr. 5 (05.03.2020): 1200. http://dx.doi.org/10.3390/en13051200.
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Latent heat thermal energy storage (LHTES) using phase change materials (PCM) is one of the most promising ways for thermal energy storage (TES), especially in lightweight buildings. However, accurate control of the phase transition of PCM is not easy to predict. For example, neglecting the hysteresis or the effect of the speed of phase change processes reduces the accuracy of simulations of TES. In this paper, the authors propose a new software module for EnergyPlus™ that aims to simulate the hysteresis of PCMs during the phase change. The new module is tested by comparing simulation results with experimental tests done in a climatic chamber. A strong consistency between experimental and simulation results was obtained, while a discrepancy error of less than 1% was obtained. Moreover, in real conditions, as a result of quick temperature changes, only a partial phase transformation of the material is often observed. The new model also allows the consideration of the case with partial phase changes of the PCM. Finally, the simulation algorithm presented in this article aims to represent a better way to model LHTES with PCM.
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Su, Yifang, Yihang Zhang, Kaifeng Lin, Guanjun Zhao, Qinzheng Yu, Zuoqi Hu und Xiongfei Tao. „Numerical Study on Resistance Change Characteristics of Phase Change Materials“. Advances in Materials Science and Engineering 2021 (06.07.2021): 1–12. http://dx.doi.org/10.1155/2021/7934173.
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Phase change materials are a type of emerging materials whose states will change under certain conditions, which then lead to changes in resistance. To study the characteristics of the phase change materials, a numerical simulation model of the resistive change unit based on the finite element method and the classic nucleation/growth theory is established, while the partial differential equations of electricity and heat conduction and the discrete formula of the finite element are also derived. According to the phase transition process of phase change materials, a crystalline-amorphous simulation model is also proposed in this paper to simulate the electrical and thermal properties and phase transition process of the resistive change unit. Simulations of the resistance change unit under single pulses with different amplitudes and widths as well as the simulations under continuous pulses are conducted in this paper. These results verify the characteristics of resistance change and can provide references for selecting the parameters of the resistance change units.
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Braga, Stefania, Alessandro Cabrini und Guido Torelli. „Transient effects in partial-RESET programming of phase-change memory cells“. Solid-State Electronics 65-66 (November 2011): 250–55. http://dx.doi.org/10.1016/j.sse.2011.06.026.
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Braga, Stefania, Alessandro Cabrini und Guido Torelli. „Experimental Analysis of Partial-SET State Stability in Phase-Change Memories“. IEEE Transactions on Electron Devices 58, Nr. 2 (Februar 2011): 517–22. http://dx.doi.org/10.1109/ted.2010.2090157.
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Stern, Keren, Nicolas Wainstein, Yair Keller, Christopher M. Neumann, Eric Pop, Shahar Kvatinsky und Eilam Yalon. „Sub-Nanosecond Pulses Enable Partial Reset for Analog Phase Change Memory“. IEEE Electron Device Letters 42, Nr. 9 (September 2021): 1291–94. http://dx.doi.org/10.1109/led.2021.3094765.
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Shi, L. P., T. C. Chong, P. K. Tan, X. S. Miao, Y. M. Huang und R. Zhao. „Study of the Partial Crystallization Properties of Phase-Change Optical Recording Disks“. Japanese Journal of Applied Physics 38, Part 1, No. 3B (30.03.1999): 1645–48. http://dx.doi.org/10.1143/jjap.38.1645.
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Peng, Chubing, und Masud Mansuripur. „Partial-response signaling for phase-change optical data storage without electronic equalization“. Applied Optics 41, Nr. 17 (10.06.2002): 3479. http://dx.doi.org/10.1364/ao.41.003479.
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Li, Yang, Yaochen Qin, Liqun Ma und Ziwu Pan. „Climate change: vegetation and phenological phase dynamics“. International Journal of Climate Change Strategies and Management 12, Nr. 4 (06.07.2020): 495–509. http://dx.doi.org/10.1108/ijccsm-06-2019-0037.
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Purpose The ecological environment of the Loess Plateau, China, is extremely fragile under the context of global warming. Over the past two decades, the vegetation of the Loess Plateau has undergone great changes. This paper aims to clarify the response mechanisms of vegetation to climate change, to provide support for the restoration and environmental treatment of vegetation on the Loess Plateau. Design/methodology/approach The Savitsky–Golay (S-G) filtering algorithm was used to reconstruct time series of moderate resolution imaging spectroradiometer (MODIS) 13A2 data. Combined with trend analysis and partial correlation analysis, the influence of climate change on the phenology and enhanced vegetation index (EVI) during the growing season was described. Findings The S-G filtering algorithm is suitable for EVI reconstruction of the Loess Plateau. The date of start of growing season was found to gradually later along the Southeast–Northwest direction, whereas the date of the end of the growing season showed the opposite pattern and the length of the growing season gradually shortened. Vegetation EVI values decreased gradually from Southeast to Northwest. Vegetation changed significantly and showed clear differentiation according to different topographic factors. Vegetation correlated positively with precipitation from April to July and with temperature from August to November. Originality/value This study provides technical support for ecological environmental assessment, restoration of regional vegetation coverage and environmental governance of the Loess Plateau over the past two decades. It also provides theoretical support for the prediction model of vegetation phenology changes based on remote sensing data.
Dissertationen zum Thema "Partial phase change"
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Quinlan, Patrick Duane. „The development of a novel integrated collector storage solar water heater (ICSSWH) using phase change materials and partial evacuation“. Thesis, Ulster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536464.
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The Integrated Collector Storage Solar Water Heater (ICSSWH) suffers significant ambient heat loss, especially during night-time and non-collection periods, due to its combined collection and storage function. A novel ICSSWH a Double Vessel Integrated Collector Storage (DVICS) comprised of two vertical concentric metal cylinders, with the resulting annulus filled with a Phase Change Material (PCM) and partial vacuum pressure, was designed to reduce thermal storage losses without compromising energy collection. The DVICS evolved through the development of 6 fabricated prototypes, including novel pockets and cowl configurations in the annulus, a polytetrafluoroethylene (PTFE) thermal break between the inner and outer vessel, elongation of the pockets to increase heat transfer to the PCM, aluminium vessel construction, differing water return arrangements, solar collection improvements to the vessel geometry, optimised pocket locations and transparent covers with insulation. The different DVICS designs were studied experimentally using thermal simulation, solar simulation and outdoor conditions at two European locations. The highest instantaneous collection efficiency was 43% and the lowest thermal losses coefficient was 0.98 Wm-2K-1. The heat transfer mechanisms were modelled using thermal resistance networks and dimensionless analysis. In addition the practical, environmental and economic considerations are presented.
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Petrášová, Anna. „Počítačové modelování teplotní hystereze při změně skupenství“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445463.
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This thesis deals with computer modeling of temperature hysteresis during phase change, namely complete and partial phase change. There is performed a review of methods for modeling temperature hysteresis based on the enthalpy method and the effective heat capacity method. In the case of complete phase change, there are several methods that use the effective heat capacity method, as well as the heat source method, which, on the contrary, is a certain analogy of the enthalpy method. The following are works dealing with modelling of partial phase change, the most interesting of which is due to the validation method of static hysteresis and the method designed by Bony and Citherlet. The second part of this thesis deals with the hysteresis behavior of the material with phase change, which is organic paraffin RT 27. The input data obtained by differential scanning calorimetry was converted to the dependence of the enthalpy on temperature. These curves was represented by piecewise linear function. In the case of partial phase transformations, a modeling method based on the methods proposed by Bonym and Citherlet was designed. An one-dimensional model enabling thermal simulation of the material was implemented in the MATLAB software environment. The results obtained with this simulation are finally compared with a model that does not consider thermal hysteresis.
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Ancellin, Matthieu. „Sur la modélisation physique et numérique du changement de phase interfacial lors d'impacts de vagues“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN010/document.
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Dans le cadre du stockage de Gaz Naturel Liquéfié (GNL) dans des réservoirs flottants, tels que les méthaniers, les contraintes imposées à la cuve par le ballotement de la cargaison doivent être quantifiées. La plupart des études expérimentales ou numériques actuelles ne prennent pas en compte la possibilité de changement de phase entre le GNL et sa vapeur lors d'un impact du liquide sur la paroi. L'objectif de cette thèse est l'ajout de ce phénomène physique dans un code de mécanique des fluides numérique pour la simulation de l'impact d'une vague déferlante sur une paroi.Dans ce but, un état de l'art des différentes modélisations possibles du changement de phase en mécanique des fluides est présenté. Il a été choisi de modéliser le changement de phase entre le liquide et le gaz à une interface franche sans hypothèse d'équilibre thermodynamique à l'interface. Un système hyperbolique de lois de conservation incluant le changement de phase interfacial hors-équilibre est présenté.Deux approches sont utilisées pour la résolution numérique de ce système. La première utilise un modèle de mélange pour décrire les mailles contenant l'interface liquide-vapeur. Dans la seconde méthode, l'interface est reconstruite et évolue de manière lagrangienne. Les deux approches sont basées sur un schéma volume fini de type Roe.L'enjeu de la simulation numérique du changement de phase interfacial est la capacité du code à gérer un rapport de densité loin de 1 et une chaleur latente élevée, qui entrainent respectivement de fortes variations de pression et de température à l'interface. L'aspect thermique est le phénomène limitant dans le cadre de la simulation d'impacts de vagues avec changement de phase. Seule une fine couche limite thermique autour de l'interface tend à revenir à l'équilibre thermodynamique liquide vapeur, ce qui limite l'effet quantitatif du changement de phaseIn the context of Liquefied Natural Gas (LNG) transportation in floating tanks, such as in LNG carriers, the constraints imposed by the sloshing of the liquid cargo on the tank have to be estimated. Most experimental and numerical studies until now do not take into account the possibility of phase change between the LNG and its vapor during the impact of liquid on the wall. The goal of this thesis is to include this physical phenomenon into a CFD code for the simulation of a breaking wave impact on a wall.A state of the art of the different modelisations of phase change in fluid mechanics is thus presented. This work focus on the modeling of phase change between the liquid and the gas at a sharp interface, without any equilibrium hypothesis. An hyperbolic system of balance laws including non-equilibrium interfacial phase change is presented.Two approaches are used to solve numerically this system. The first one relies on a mixture model for the description of the finite volume cells containing the interface, whereas in the second approach the interface is reconstructed and evolves in a lagrangian way. Both methods are based on a Roe-type finite volume scheme.The challenge of the numerical simulation of interfacial phase change is the capacity of the code to deal with density ratio far from 1 and high latent heat, as the lead to high temperature and pressure variations at the interface. The thermal aspect is the limiting phenomenon in the frame of wave impact simulation with phase change. Only a thin boundary layer around the interface tends to return to thermodynamical equilibrium, thus limiting the quantitative effect of phase change
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Kuravi, Sarada. „Numerical Study of Encapsulated Phase Change Material (EPCM) Slurry Flow in Microchannels“. Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4093.
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Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m width and 533 [micro]m height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
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Delhorme, Maxime. „Thermodynamics and Structure of Plate-Like Particle Dispersions“. Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00818964.
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A considerable amount of mineral particles are found to have a plate-like shape. The work in this thesis concerns theoretical investigations, using a Monte Carlo method, of the properties of such particles in aqueous solutions. The objectives were first to create a model that could capture the essential physics of clay suspensions and also to understand the role of thermodynamics in certain chemical processes. For all investigations, the results are related to experimental studies. The acid-base behavior of clays have been studied, using the primitive model, and an excellent agreement between simulated and experimental results was found. The formation of gel phases as a function of the charge anisotropy have also been investigated. Liquid-gel and sol-gel transitions are found to occur for high and moderate charge anisotropy, respectively. These transitions were also found to be size and salt dependent. In absence of charge anisotropy, a liquid-glass transition is reported. The formation of smectic and columnar liquid crystals phases with plate-like particles has been found to be favored by a strong charge anisotropy, in opposition to what was observed for nematic phases. New liquid-crystal phases were also reported. The stability and growth of nanoplatelets is discussed. It was found that the internal Coulombic repulsion could be the cause of the limited growth of C-S-H platelets. The influence of thermodynamics on the agregation mode of such platelets was also investigated
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Li, Yaofa. „Experimental studies of Marangoni convection with buoyancy in simple and binary fluids“. Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53893.
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The flow in a layer of volatile fluid driven by a horizontal temperature gradient is a fundamental transport model for numerous evaporative passive cooling applications. When a thin film of a volatile liquid is subject to a horizontal temperature gradient, changes in the surface tension at the free surface lead to Marangoni stresses that drive the flow. In a thicker liquid layer, the flow is also affected by buoyancy. This thesis describes experimental studies of convection driven by a combined action of Marangoni stresses and buoyancy in simple and binary volatile liquid layers confined in a sealed rectangular cavity heated at one end and cooled at the other. Experiments with varying concentrations of noncondensables (i.e., air) ca were performed to investigate their effect on the phase change and heat and mass transport.
In the simple liquid, thermocapillary stresses drive the liquid near the free surface away from the heated end. Varying ca is shown to strongly affect the stability of this buoyancy-thermocapillary flow for Marangoni numbers Ma = 290 - 3600 and dynamic Bond numbers BoD = 0.56 - 0.82: removing air suppresses transition to multicellular and unsteady flow. The results are compared with numerical simulations and linear stability analysis. In the binary liquid considered here, a methanol-water (MeOH-H2O) mixture, solutocapillary stresses drive the flow near the free surface towards the heated end. Four distinct flow regimes are identified for this complex flow driven by thermocapillarity, solutocapillarity, and buoyancy, and are summarized in a flow regime map as a function of ca and the liquid composition (MeOH concentration). At low ca, solutocapillary effects are strong enough to drive the liquid near the free surface towards the heated end over the entire liquid layer, suggesting that binary-fluid coolants could significantly reduce film dryout.
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Reinhardt, Bruno. „Compréhension et évaluation du comportement des suspensions gaz-solide à forte charge dans les techniques de séparation aéraulique“. Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/a37df539-7e5e-4347-b8e6-7f15fd2cfb0f.
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L'optimisation du fonctionnement des cyclones peut être réalisée à partir d'études expérimentales sur maquettes. La première partie traite de la similitude: des caractérisations aérodynamiques (à vide) dans deux cyclones homothétiques mettent en évidence deux types d'écoulements et une similitude partielle. Dans une seconde partie, nous exposons les résultats des mesures de vitesse et de concentration qui permettent d'analyser la structure de l'écoulement. Nous présenterons dans la dernière partie les calculs réalisés à l'aide d'un code de simulation numérique.
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Tsafack, Chetsa Ghislain Landry. „System Profiling and Green Capabilities for Large Scale and Distributed Infrastructures“. Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00946583.
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Nowadays, reducing the energy consumption of large scale and distributed infrastructures has truly become a challenge for both industry and academia. This is corroborated by the many efforts aiming to reduce the energy consumption of those systems. Initiatives for reducing the energy consumption of large scale and distributed infrastructures can without loss of generality be broken into hardware and software initiatives.Unlike their hardware counterpart, software solutions to the energy reduction problem in large scale and distributed infrastructures hardly result in real deployments. At the one hand, this can be justified by the fact that they are application oriented. At the other hand, their failure can be attributed to their complex nature which often requires vast technical knowledge behind proposed solutions and/or thorough understanding of applications at hand. This restricts their use to a limited number of experts, because users usually lack adequate skills. In addition, although subsystems including the memory are becoming more and more power hungry, current software energy reduction techniques fail to take them into account. This thesis proposes a methodology for reducing the energy consumption of large scale and distributed infrastructures. Broken into three steps known as (i) phase identification, (ii) phase characterization, and (iii) phase identification and system reconfiguration; our methodology abstracts away from any individual applications as it focuses on the infrastructure, which it analyses the runtime behaviour and takes reconfiguration decisions accordingly.The proposed methodology is implemented and evaluated in high performance computing (HPC) clusters of varied sizes through a Multi-Resource Energy Efficient Framework (MREEF). MREEF implements the proposed energy reduction methodology so as to leave users with the choice of implementing their own system reconfiguration decisions depending on their needs. Experimental results show that our methodology reduces the energy consumption of the overall infrastructure of up to 24% with less than 7% performance degradation. By taking into account all subsystems, our experiments demonstrate that the energy reduction problem in large scale and distributed infrastructures can benefit from more than "the traditional" processor frequency scaling. Experiments in clusters of varied sizes demonstrate that MREEF and therefore our methodology can easily be extended to a large number of energy aware clusters. The extension of MREEF to virtualized environments like cloud shows that the proposed methodology goes beyond HPC systems and can be used in many other computing environments.
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BOUDJENANE, NASR EDDINE. „Ecoulement des melanges liquides-solides en conduites horizontale et verticale : perte de charge et reduction de frottement“. Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13148.
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Etude de la perte de charge et du mode d'ecoulement pour des melanges liquide solide en conduites horizontales et verticales. On met en evidence deux categories de particules : particules fines a ecoulement heterogene. On obtient une reduction de frottement de 45 % en ajoutant une quantite de particules fines au melange eau et grosses particules
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Nasani, Ahmad Muntaser. „Etude des phénomènes électrofluidodynamiques sur les gaz empoussiérés en écoulement turbulent : application au transport pneumatique“. Poitiers, 1987. http://www.theses.fr/1987POIT2307.
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Analyse de l'influence de certains parametres sur le processus de tranfert de charges electriques au moment du contact d'une particule solide avec une plaque metallique. Etude de la charge d'impact en fonction de l'inclinaison de la plaque, de sa position et de sa charge initiale. Analyse theorique de l'ensemble des phenomenes d'ehd lies au transport pneumatique, en particulier des chutes de pression. Resultats experimentaux dans le cas de deux phases d'ecoulement : ecoulement en phase diluee et ecoulement en phase dense discontinue
Bücher zum Thema "Partial phase change"
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Gupta, Joyeeta. Climate Change and the Future of International Order. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198828945.003.0003.
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On the basis of the scientific consensus on the dangers of climate change, this issue emerged as a partial order in the 1990s and was developed as an international regime in five phases. This chapter analyzes how the functional order evolved throughout the phases, and assesses the respective approaches, actors, and implications. Major steps for the development of the regime were the Kyoto Protocol (KP) and the Paris Agreement (PA) though the international agreements at times and the fight against climate change in general lack the full support from several key states like the USA, China, Japan, and Russia. The order lost its predictability but retains its legitimacy, leading, however, to questionable prospects on its effectiveness. Therefore, its greatest challenge may be to change the approach from international legal action to the restructuring of societies.
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Gomez Arana, Arantza. The first attempt to negotiate the association agreement. Manchester University Press, 2017. http://dx.doi.org/10.7228/manchester/9780719096945.003.0006.
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This chapter aims to explain the phase in EU-Mercosur relations which negotiated the association agreement without reaching a successful ending. Both parties developed those negotiations under the European Mercosur Interregional Cooperation Agreement (EMIFCA). It was agreed that this agreement would be carried out in two phases. The first phase related to the preparation of the ground for future negotiations by comparing standards, statistical systems, trade procedures, whilst the second phase focussed on trade liberalization. The second phase of this agreement was also focussed on the actual negotiations. In the end, both parties were unable to reach an agreement and the negotiations were stopped in October 2004. This chapter will focus on the period up until the period where the EU became set on developing a political partnership with Brazil. In doing so, this decision marked the beginning of a new stage in history of EU policy towards Mercosur. By looking at how these two parts of the policy were developed, and how far both sides went in both their statements and actions it will be possible to discuss the level of engagement on the EU side towards Mercosur. It seems that there were actors within the EU willing to both increase and decrease the level of “ambition” and “commitment”. Also, Mercosur countries helped to overcome some of the obstacles and this should be considered in order not to attribute the whole outcome solely to EU behaviour. The EU developed the association agreement towards Mercosur at this stage because of the efforts of the Commissioner in charge of the policy until 1999.
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Epstein, Ben. Political Choice. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190698980.003.0004.
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Chapter 4 explains the concept of political choice, the second and most important phase of the political communication cycle (PCC). The political choice phase is the process in which political actors choose if and when to incorporate new information and communications technologies (ICTs) into their communication strategies. This chapter details the process that political actors or organizations go through when determining whether to innovate and helps to identify characteristics of those parties that are more likely to innovate earlier than others, known as innovativeness. Political choice is the behavioral component of the political communication cycle. These innovation decisions are the primary determinants regarding if and how ICT innovations are used to change political communication activity. Therefore, political choice is the most important phase of the PCC, differentiating political communication change from social and societal communication change more broadly.
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Aveyard, Bob. Surfactants. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198828600.001.0001.
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Characteristically, surfactants in aqueous solution adsorb at interfaces and form aggregates (micelles of various shapes and sizes, microemulsion droplets, and lyotropic liquid crystalline phases). This book is about the behaviour of surfactants in solution, at interfaces, and in colloidal dispersions. Adsorption at liquid/fluid and solid/liquid interfaces, and ways of characterizing the adsorbed surfactant films, are explained. Surfactant aggregation in systems containing only an aqueous phase and in systems with comparable volumes of water and nonpolar oil are each considered. In the latter case, the surfactant distribution between oil and water and the behaviour of the resulting Winsor systems are central to surfactant science and to an understanding of the formation of emulsions and microemulsions. Surfactant layers on particle or droplet surfaces can confer stability on dispersions including emulsions, foams, and particulate dispersions. The stability is dependent on the surface forces between droplet or particle surfaces and the way in which they change with particle separation. Surface forces are also implicated in wetting processes and thin liquid film formation and stability. The rheology of adsorbed films on liquids and of bulk colloidal dispersions is covered in two chapters. Like surfactant molecules, small solid particles can adsorb at liquid/fluid interfaces and the final two chapters focus on particle adsorption, the behaviour of adsorbed particle films and the stabilization of Pickering emulsions.
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Mitrović, Moreno. Configurational change in Indo-European coordinate constructions. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198747307.003.0002.
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This chapter presents a case study of word order change in coordinate constructions across a wide range of Indo-European languages. Early Indo-European languages had two available patterns of coordination at their disposal: one in which the coordinating particle was placed in first and another in which it was placed in the second position with respect to the second coordinand (‘Wackernagel effect’). Diachronically, the two competing configurations reduce to a single winning one, namely the head-initial one that all contemporary Indo-European languages retained. This is accounted for as the result of the loss of ‘Wackernagel movement’ and the development of a lexicalized J(unction)-morpheme. Resting on the notion of Junction, the analysis succeeds in explaining the bimorphemicity signature of initial conjunctions by deriving the morpheme count as a fusional exponent of two functional heads. The analysis stands on the assumption that narrow- and postsyntactic processes operate in derivationally delimited chunks, qua phases.
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Walsh, Bruce, und Michael Lynch. Using Molecular Data to Detect Selection: Signatures from Recent Single Events. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830870.003.0009.
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Different types and phases of a selective sweep (hard, soft, partial, polygenic) generate different patterns of departures from neutrality, and hence require different tests. It is thus not surprising that a large number of tests have been proposed that use sequence information to detect ongoing, or very-recently completed, episodes of selection. This chapter critically reviews over 50 such tests, which use information on allele-frequency change, linkage disequilibrium patterns, spatial allele-frequency patterns, site-frequency spectrum data, allele-frequency spectrum data, and haplotype structure. This chapter discusses the domain of applicability for each test, and their strengths and weaknesses. Finally, this chapter examines application of these methods in the search for recent, or ongoing, selection in humans and for genes involved in the domestication process in plants and animals.
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Kenyon, Ian R. Quantum 20/20. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198808350.001.0001.
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This text reviews fundametals and incorporates key themes of quantum physics. One theme contrasts boson condensation and fermion exclusivity. Bose–Einstein condensation is basic to superconductivity, superfluidity and gaseous BEC. Fermion exclusivity leads to compact stars and to atomic structure, and thence to the band structure of metals and semiconductors with applications in material science, modern optics and electronics. A second theme is that a wavefunction at a point, and in particular its phase is unique (ignoring a global phase change). If there are symmetries, conservation laws follow and quantum states which are eigenfunctions of the conserved quantities. By contrast with no particular symmetry topological effects occur such as the Bohm–Aharonov effect: also stable vortex formation in superfluids, superconductors and BEC, all these having quantized circulation of some sort. The quantum Hall effect and quantum spin Hall effect are ab initio topological. A third theme is entanglement: a feature that distinguishes the quantum world from the classical world. This property led Einstein, Podolsky and Rosen to the view that quantum mechanics is an incomplete physical theory. Bell proposed the way that any underlying local hidden variable theory could be, and was experimentally rejected. Powerful tools in quantum optics, including near-term secure communications, rely on entanglement. It was exploited in the the measurement of CP violation in the decay of beauty mesons. A fourth theme is the limitations on measurement precision set by quantum mechanics. These can be circumvented by quantum non-demolition techniques and by squeezing phase space so that the uncertainty is moved to a variable conjugate to that being measured. The boundaries of precision are explored in the measurement of g-2 for the electron, and in the detection of gravitational waves by LIGO; the latter achievement has opened a new window on the Universe. The fifth and last theme is quantum field theory. This is based on local conservation of charges. It reaches its most impressive form in the quantum gauge theories of the strong, electromagnetic and weak interactions, culminating in the discovery of the Higgs. Where particle physics has particles condensed matter has a galaxy of pseudoparticles that exist only in matter and are always in some sense special to particular states of matter. Emergent phenomena in matter are successfully modelled and analysed using quasiparticles and quantum theory. Lessons learned in that way on spontaneous symmetry breaking in superconductivity were the key to constructing a consistent quantum gauge theory of electroweak processes in particle physics.
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Holmberg, Sören, und Per Hedberg. The Will of the People? Swedish Nuclear Power Policy. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198747031.003.0010.
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Sweden started its nuclear programme in the early 1950s. Initially it was generally welcomed as modernization and even supported by environmentalists. The issue became more contested in the 1970s, when protests began and the Centre Party turned anti-nuclear. In the 1980s, the phasing out of nuclear energy until 2010 was decided as a consequence of a referendum. In 2010, however, the parliament decided to allow building a new generation of nuclear power plants. After the Fukushima disaster a new phase of nuclear energy confinement began in 2014 as a consequence of a Red-Green coalition coming to power. Over the years most Swedish parties have reversed their positions on the nuclear power issue. Policy reversals were triggered by party competition and government replacement and reflected changes in public opinion as well as coalition politics.
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Boudreau, Joseph F., und Eric S. Swanson. Quantum field theory. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198708636.003.0024.
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Markov chain Monte Carlo techniques are developed to compute properties of a variety of quantum field theories. The method is introduced with a simple scalar field theory and used to evaluate the particle spectrum and phase diagram for parity symmetry breaking. The technique of micorcanonical updating is introduced to increase efficiency. The important topic of gauge theory is then introduced via the gauged Z2 model. Development of the gauge theory formalism continues with Abelian gauge theory in two dimensions. The interaction between static charges is computed and compared to the exact result. The string tension in nonableian SU(2) gauge theory is explored with the aid of the renormalization group, which gives an entrée to a discussion of the Higgs mechanism. Finally, the formalism for including fermions is briefly reviewed.
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Cardinale, Daniela, und Carlo Maria Cipolla. Anthracycline-related cardiotoxicity: epidemiology, surveillance, prophylaxis, management, and prognosis. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0290.
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Anthracycline-induced cardiotoxicity is of considerable concern, as it may compromise the clinical effectiveness of treatment, affecting both quality of life and overall survival in cancer patients, independently of the oncological prognosis. It is probable that anthracycline-induced cardiotoxicity is a unique and continuous phenomenon starting with myocardial cell injury, followed by progressive left ventricular ejection fraction (LVEF) decline that, if disregarded and not treated progressively leads to overt heart failure. The main strategy for minimizing anthracycline-induced cardiotoxicity is early detection of high-risk patients and prompt prophylactic treatment. According to the current standard for monitoring cardiac function, cardiotoxicity is usually detected only when a functional impairment has already occurred, precluding any chance of its prevention. At present, anthracycline-induced cardiotoxicity can be detected at a preclinical phase, very much before the occurrence of heart failure symptoms, and before the LVEF drops by measurement of cardiospecific biochemical markers or by Doppler myocardial and deformation imaging. The role of troponins in identifying subclinical cardiotoxicity and treatment with angiotensin-converting enzyme inhibitors, in order to prevent LVEF reduction is an effective strategy that has emerged in the last 15 years. If cardiac dysfunction has already occurred, partial or complete LVEF recovery may still be achieved if cardiac dysfunction is detected early after the end of chemotherapy and heart failure treatment is promptly initiated.
Buchteile zum Thema "Partial phase change"
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Meyer, Gunter H. „The Numerical Solution of Phase Change Problems“. In Structure and Dynamics of Partially Solidified Systems, 141–56. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3587-7_10.
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Wollkind, D. J. „Nonlinear Analyses of Phase Change and Crystal Growth Phenomena“. In Structure and Dynamics of Partially Solidified Systems, 81–94. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3587-7_5.
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Joshi, C., A. Caldwell, P. Muggli, S. D. Holmes und V. D. Shiltsev. „Outlook for the Future“. In Particle Physics Reference Library, 797–825. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-34245-6_12.
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AbstractThe charge separation between electrons and ions that exists within an electron plasma density wave can create large electric fields. In 1979 Tajima and Dawson first recognized that the longitudinal component of the field of a so-called “relativistic” wave (one propagating with a phase velocity close to c), could be used to accelerate charged particles to high energies in a short distance [1]. The accelerating gradient of such a plasma wave, Eo, can be approximated—assuming a total separation of electrons and ions in such a wave with wavelength λp = 2πc/ωp—as
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Bhattacharya, Rabi. „Phase Changes with Time and Multi-Scale Homogenizations of a Class of Anomalous Diffusions“. In Probability and Partial Differential Equations in Modern Applied Mathematics, 11–26. New York, NY: Springer New York, 2005. http://dx.doi.org/10.1007/978-0-387-29371-4_2.
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Robson, Robert E., Ronald D. White und Malte Hildebrandt. „Basic Theoretical Concepts: Phase and Configuration Space“. In Fundamentals of Charged Particle Transport in Gases and Condensed Matter, 15–26. Boca Raton, FL : CRC Press, Taylor & Francis Group, [2017] |: CRC Press, 2017. http://dx.doi.org/10.4324/9781315120935-2.
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Hasegawa, Takayo, Hiroki Kobayashi, Hiroaki Kumakura, Hitoshi Kitaguchi und Kazumasa Togano. „Phase Changes and Solidification Mechanism of Bi2Sr2CaCu2Ox from Partially Molten State“. In Advances in Superconductivity VI, 707–10. Tokyo: Springer Japan, 1994. http://dx.doi.org/10.1007/978-4-431-68266-0_158.
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Anderson, Greg M., und David A. Crerar. „Partial and Apparent Molar Properties“. In Thermodynamics in Geochemistry. Oxford University Press, 1993. http://dx.doi.org/10.1093/oso/9780195064643.003.0013.
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To this point we have developed a method of dealing with processes involving for the most part material (phases) of fixed composition. To progress further, we need to develop ways of dealing with the properties of dissolved substances, and with phases of variable composition. In other words, we need to deal with solutions. We have seen that the properties of homogeneous substances (usually, but not necessarily pure) are either total or molar properties (neglecting, as usual, specific properties). But obviously substances change drastically when they dissolve. How can we obtain properties for the dissolved substance alone, as opposed to the solution of which it is a part? Properties of dissolved substances are called apparent molar and partial molar properties, and these are the tools we need to discuss the thermodynamics of solutions in the following chapters. Partial molar properties are defined by partial derivatives (equations 2.22,9.7), which does not provide a very easy route to understanding them. There is however a highly intuitive way of thinking about partial molar properties. We will use volume as an example because it is readily visualized, but all relations derived can be used equally well for any other state variable. It will be useful to begin by realizing that we can also use derivatives to define molar properties of pure phases; this mathematical treatment is discussed in Chapter 2. Consider first the volume of a crystalline phase such as NaCl. The volume occupied by the salt, V, varies directly with the quantity of salt, so that a plot of volume versus number of moles of salt is a straight line (Figure 9.1).
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Bulatov, Vasily, und Wei Cai. „Phase Field Method“. In Computer Simulations of Dislocations. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198526148.003.0016.
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The phase field method (PFM) can be used as an approach to dislocation dynamics simulations alternative to the line DD method discussed in Chapter 10. The degrees of freedom in PFM are continuous smooth fields occupying the entire simulation volume, and dislocations are identified with locations where the field values change rapidly. As we will see later, as an approach to dislocation dynamics simulations PFM holds several advantages. First, it is easier to implement into a computer code than a line DD model. In particular, the complex procedures for making topological changes (Section 10.4) are no longer necessary. Second, the implementation of PFM can take advantage of well-developed and efficient numerical methods for solving partial differential equations (PDEs). Another important merit of PFM is its applicability in a wide range of seemingly different situations. For example, it is possible to simulate the interaction and co-evolution of several types of material microstructures, such as dislocations and alloying impurities, within a unified model. PFM has become popular among physicists and materials scientists over the last 20 years, but as a numerical method it is not new. After all, it is all about solving PDEs on a grid. Numerical integration of PDEs is a vast and mature area of computational mathematics. A number of efficient methods have already been developed, such as the finite difference method [121], the finite element method [122], and spectral methods [123], all of which have been used in PFM simulations. The relatively new aspects of PFM are associated with the method’s formulation and applications, which are partly driven by the growing interest in understanding material microstructures. In Section 11.1, we begin with the general aspects of PFM demonstrated by two simple applications of the method not related to dislocations. Section 11.2 describes the elements required to adapt PFM to dislocation simulations. There we will briefly venture into the field of micromechanics and consider the concept of eigenstrain. The elastic energy of an arbitrary eigenstrain field is derived in Section 11.3. Section 11.4 discusses an example in which the PFM equations for dislocations are solved using the fast Fourier transform method.
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Acosta-Najarro, Dwight, Ismael A. Garduño-Wilches, Maria de la Luz Olvera und Arturo Maldonado. „TiO2 Thin Films Produced by Ultrasonic-Agitation Assisted Sol-Gel for Propane Gas Sensor“. In Thin Films [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95528.
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TiO2 films were deposited by the sol–gel dip coating method assisted by ultra sonic agitation, for their use as propane gas sensors. XRD anlaysis revealed the TiO2 anatase phase for all samples. The film thickness was controlled with the number of the dip-coating immersion cycles, obtaining thicknesses from 10 to 130 nm and a growing rate of 18 nm per immersion. Surface morphology shows that films grow more compact and densely packed as the number of immersion cycles increase. Gas sensing studies indicate that work temperatures above 300°C are needed for sensing activation of the films. Gas sensors sensitivity as a function of propane concentration and film thickness revealed a two-regime behavior: for partial pressures of propane above 400 ppm the sensitivity is not dependent of the film thickness, whereas it is dependent on this parameter at lower partial pressures. Such behavior is attributed to a space charge region and a change in surface structure. For the low concentration regime, the maximum sensitivity was obtained for a film thickness of 110 nm or 5 inmersions.
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Skoko, Željko, und Stanko Popović. „Microstructure of Al-Cu, Al-Zn, Al-Ag-Zn, and Al-Zn-Mg Alloys“. In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000172.
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The precipitation phenomena and their connection with the microstructure of several Al alloys (Al-Cu, Al-Zn, Al-Ag-Zn, Al-Zn-Mg) are described with respect to the concentration and applied thermal treatment. The alloys were rapidly quenched or slowly cooled from a temperature higher than the solid solution temperature to room temperature. Both quenched-aged and slowly cooled alloys were heated from room temperature to the solid solution state and cooled back to room temperature, and their microstructure and precipitation phenomena were followed in situ by X-ray powder diffraction, e.g., anisotropy of thermal expansion, phase transitions, thermal hysteresis in phase transitions, change of precipitate shape, partial or complete dissolution of precipitates in the matrix, and formation of solid solution. It has been shown that the microstructure strongly depends on the previous thermal history of the alloys.
Konferenzberichte zum Thema "Partial phase change"
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Braga, S., A. Sanasi, A. Cabrini und G. Torelli. „Modeling of partial-RESET dynamics in Phase Change Memories“. In ESSDERC 2010 - 40th European Solid State Device Research Conference. IEEE, 2010. http://dx.doi.org/10.1109/essderc.2010.5618176.
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Braga, Stefania, Alessand Cabrini und Guido Torelli. „Data retention of partial-set states in phase change memories“. In 2010 IEEE 3rd International Nanoelectronics Conference (INEC). IEEE, 2010. http://dx.doi.org/10.1109/inec.2010.5424897.
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Roday, Anand P., und Michael J. Kazmierczak. „Phase-Change in Finite Slabs With Time-Dependent Convective Boundary Conditions“. In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56734.
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The heat balance integral method is used to solve one-dimensional phase-change problem in a finite slab with time-dependent convective boundary condition, [T∞,1(t)], applied at the left face. The temperature, T∞,1(t), decreases linearly with time; the other face of the slab is subjected to a constant convective boundary condition with T∞,2 held fixed at the ambient temperature. Two initial conditions are investigated: temperature of the solid below the melting point (subcooled), and initially at the fusion temperature (Tf). The temperature, T∞,1(t) at time t = 0 is so chosen such that convective heating takes place and the slab begins to melt (i.e., T∞,1(0)> Tf> T∞,2). Thus the solid-liquid interface proceeds forward to the right. As time continues, and T∞,1(t) decreases with time, the phase-change front slows, stops, and may even reverse direction. Hence this problem features sequential melting and freezing of the slab with partial penetration of the solid-liquid front before reversal of the phase-change process. It should, however, be noted that the study is limited to only one solid-liquid interface at any given time during the phase-change process (either melting or freezing) and that slight subcooling of the melt is allowed. The effect of varying the Biot number at the right face of the slab, for both the initial conditions, is also investigated to determine its impact on the growth/recession of the solid-liquid interface. Temperature profiles in both regions (liquid and solid) are reported in detail. The effect of a slower decay rate of T∞,1(t) on the phase-change process is also analyzed for the initial condition of the slab being at the fusion temperature.
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Xiao, Bin, und Yuwen Zhang. „Analysis of Melting in a Single-Component Metal Powder Bed Subject to Constant Heat Flux Heating“. In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56362.
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To model Selective Laser Sintering (SLS) of single-component metal powders, melting of a subcooled powder bed with single-component metal powder is investigated analytically. Since laser processing of metal powder is a very rapid process, the liquid and solid phases of a partially molten powder particle may have different temperatures: the temperature in the liquid phase is higher than the melting point, and the temperature in the solid phase is below the melting point. Therefore, the local temperature of regions with partial molten particles is within a range of temperature adjacent to the melting point, instead of at melting point. In addition, the powder bed experiences a significant density change during melting. Therefore, melting of a metal powder bed can be modeled as a melting that occurs in a range of temperature with significant density change. The temperature distributions and locations of the various interfaces were obtained by solving the governing equations for solid, liquid and mushy zones in a one-dimensional system using an integral approximate method. The effects of porosity, sub-cooling, dimensionless thermal conductivity of gas, and dimensionless heat flux on the surface temperature and locations of the interfaces were investigated.
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Lan, Zhong, Quan Xue, Xuehu Ma, Di Wang, Kejian Cao und Zongchang Zhao. „Theoretical Study on Aggregation of Nuclei-Containing Gas Phase“. In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-5056.
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Haze is a kind of typical heterogeneous nucleation phenomenon in gas phase condensation process. The existence of dust nucleus may induce water molecule aggregation among vapor phase under a certain humidity. In this article, we try to use Density Functional Theory simulation to explore the evolution mechanism of water molecule aggregation influenced by condensation nucleus from the perspective of molecules assembling. We can get the following results: the subcooling degree and physicochemical properties of nucleation center affect the hydrogen bond within the water clusters and the transformation energy barrier of water molecule aggregation tendency. Water vapor begins to heterogeneously condense or forms aggregation humidity in a certain condition based on the center of condensation nuclei. The analysis shows that the effect law of the degree and scale of aggregation or phase transition are influenced by the change of gas phase partial pressure, supersaturated degree along with particle properties. As the energy barrier of nucleation free energy decreases, the formation of water clusters will be easier.
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West, Glen O., und Kent S. Udell. „Heat Transfer During Heating and Cooling of a Packed Bed Comprised of Encapsulated Phase Change Material“. In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4953.
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Phase change materials (PCMs) are attractive components of thermal energy storage systems due to their high energy densities and the relatively small temperature differences needed for effective charging and discharging. In this study, experimental data were examined in order to better understand energy exchange in packed beds and porous media comprised of solid/liquid phase change capsules. Air was used as the heat transfer fluid; hot air was injected in order to drive the melting process, while cold air was injected to accomplish freezing or solidification of the PCM. Theory was developed to describe the temperature variations throughout the bed. Temperatures in the bed were found to vary exponentially near the phase change fronts. For cold air injection into a bed initially above the phase change temperature, a second wave was observed ahead of the phase change front that can be described as a broadening traveling thermal wave due to diffusion/dispersion. For hot air injection into a packed bed of solidified PCM capsules initially at a temperature below the phase change temperature, the thermal waves in the cold region showed isotherm velocity retardation due to incomplete thawing. A shrinking core model of the melting or solidification of the PCM in the capsules was developed to document the internal heat transfer constraints within the capsules. The results of that study support the conclusion that slower wave velocities occur due to partial melting.
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Fan, Jintu, und Xiaoyin Cheng. „A Numerical and Experimental Study of Heat and Moisture Transfer With Phase Change and Mobile Condensates in Fibrous Insulation“. In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47597.
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This paper reports on an improved model of coupled heat and moisture transfer with phase change and mobile condensates in fibrous insulation. The new model considered the moisture movement induced by the partial water vapor pressure, a super saturation state in condensing region as well as the dynamic moisture absorption of fibrous materials and the movement of liquid condensates. The results of the new model were compared and found in good agreement with the experimental ones. Numerical simulation was carried using the model to investigate the effect of various material parameters on the transport phenomena.
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Helmns, Andrea, und Van P. Carey. „Modeling of Heat Transfer and Energy Efficiency Performance of Transient Cold Storage in Phase Change Thermal Storage Components“. In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7237.
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This paper presents a design analysis framework for a transient cold storage unit that uses solid-liquid phase change for thermal storage. The analytical framework developed in this study establishes non-dimensional parameters that dictate the energy efficiency of the transient energy input and extraction processes, and specifies the links between physical parameters for the system and dimensionless parameters. The resulting governing equations in non-dimensional form are partial differential equations that can be solved numerically. Solutions of the equations predict the thermodynamic efficiency (effectiveness) of the energy storage and retrieval processes, and the time required to input or extract energy from storage for specified values of the dimensionless parameters. The paper illustrates how a high efficiency design target can be established for specified operating conditions using this framework. Application of this framework to a typical example application involving cold thermal storage is described, and the usefulness of this methodology is demonstrated. The use of this methodology for predicting the performance of cold thermal storage for a broad range of potential applications is also discussed.
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Gao, Lin, und Yiping Dai. „Rotor Dynamic Analysis on Partial Admission Control Stage in a Large Power Steam Turbine“. In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22608.
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Partial admission is used widely for steam turbines to match their output power to the load demand. The occurrences or thresholds of most self-induced low-frequency vibrations are under partial admission conditions. But the destabilizing forces which cause rotor instability are seldom investigated under partial admission conditions especially for large power steam turbines. Full 3D CFD model is built for the control stage of a 600 MW steam turbine applying commercial codes. N-S equations are solved to investigate the flow fields in the control stage including all the blade passages and the labyrinth seal over the shroud. Interesting flow distributions are observed for the seal spaces at partial admission conditions. A correction formula is presented for partial admission labyrinth seal based on the classical one and a method is discussed for the estimation of partial-admission phase-angle-dependent stiffness coefficients. The destabilizing forces acting on the rotor system are calculated for different eccentricity angles and are compared with those under the concentric condition. The stiffness coefficients are solved under typical partial admission conditions. They are found to change dramatically with the phase angle. The results may be helpful for a deep understanding of the low-frequency variation problems of large power steam turbines under partial admission conditions.
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Mucci, Alberto, Foster Kwame Kholi, Man Yeong Ha, Jason Chetwynd-Chatwin und June Kee Min. „Numerical Analysis of the Phase-Change Heat Transfer Inside a Pulsating Heat Pipe With Overcritical Number of Turns“. In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15332.
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Abstract The Pulsating Heat Pipe (PHP) is a promising device in the family of heat pipes. With no need for a wick, they exhibit a high heat transfer to weight ratio. Moreover, the wickless design removes limits commonly associated with conventional heat pipes, increasing the maximum power transfer per single heat pipe. These peculiarities make it an ideal candidate for many high power applications. Nonetheless, there is though only partial knowledge on the driving mechanism, which restricts prediction accuracy. Most Pulsating Heat Pipe studies rely on experiments to test configurations, while simulations usually depend on semi-empirical correlations or adaptations of reduced theoretical models. Experiments provide detailed data for a particular geometry in lab fixed conditions, but it offers limited flexibility to test alternative configurations. Semi-empirical models use previous experimental data to create non-dimensional formulations. Though approaching an increased set of conditions, correlations apply with reasonable accuracy only to a small range, outside of which the prediction ability progressively falls. High order numerical analysis such as Computational Fluid Dynamics (CFD) modeling could potentially provide full visualization, but due to the complex flow behavior, previous studies used this method only in simple configurations with a small number of turns. The present research will expand the potential of this modeling technique by presenting the CFD analysis of a complex Pulsating Heat Pipe configuration. The importance of this study lies in the fact that this configuration, with a number of turns greater than a critical parameter, shows a reduced sensitivity to gravity and is therefore particularly important for applications where restrictions on installations make the positioning sub-optimal. The research simulates using a CFD commercial software a two-dimensional Pulsating Heat Pipe with sixteen turns. The heat pipe, with a 2 mm internal diameter, is filled with water at 50% of mass. To visualize the oscillation pattern of liquid and vapor slugs and plugs inside the Pulsating Heat Pipe, the model performs a transient analysis on the device. A Volume of Fluid (VOF) solver for multiphase analysis, coupled with the Lee model for evaporation and condensation mass transfer, calculates the interactions between the liquid and the gas phase inside the tube. The study follows the geometric and operational conditions from previous experiments. The analysis regards a Pulsating Heat Pipe operating in a vertical position with the condenser section placed in the upper sector. During the initial operations, the system flow distribution fluctuates between different flow modes as the fluid slugs and plugs structure forms. After stabilizing the heat transfer results well agree with the tested values. Moreover, the increased resolution allows us to fully visualize the internal operation, retrieving additional information on the temperature and ratio of liquid and gas phase along the heat pipe.
Berichte der Organisationen zum Thema "Partial phase change"
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Choi, E., Y. I. Cho und H. G. Lorsch. Effects of emulsifier on particle size of a phase change material in a mixture with water. Office of Scientific and Technical Information (OSTI), Juni 1991. http://dx.doi.org/10.2172/6792238.
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Choi, E., Y. I. Cho und H. G. Lorsch. Effects of emulsifier on particle size of a phase change material in a mixture with water. Progress report, March 31, 1991--June 30, 1991. Office of Scientific and Technical Information (OSTI), Juni 1991. http://dx.doi.org/10.2172/10148563.
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