Готові списки джерел за темами / One-Dimensional Bose Gases

Добірка наукової літератури з теми "One-Dimensional Bose Gases"

Автор: Grafiati

Опубліковано: 14 березня 2023

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Статті в журналах з теми "One-Dimensional Bose Gases"

Yukalov, V. I., and M. D. Girardeau. "Fermi-Bose mapping for one-dimensional Bose gases." Laser Physics Letters 2, no. 8 (August 1, 2005): 375–82. http://dx.doi.org/10.1002/lapl.200510011.

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Baldovin, F., A. Cappellaro, E. Orlandini, and L. Salasnich. "Nonequilibrium statistical mechanics in one-dimensional bose gases." Journal of Statistical Mechanics: Theory and Experiment 2016, no. 6 (June 13, 2016): 063303. http://dx.doi.org/10.1088/1742-5468/2016/06/063303.

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Yngvason, Jakob, Elliott H. Lieb, and Robert Seiringer. "One-Dimensional Behavior of Dilute, Trapped Bose Gases." Communications in Mathematical Physics 244, no. 2 (January 1, 2004): 347–93. http://dx.doi.org/10.1007/s00220-003-0993-3.

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Cazalilla, M. A., A. F. Ho, and T. Giamarchi. "Interacting Bose gases in quasi-one-dimensional optical lattices." New Journal of Physics 8, no. 8 (August 30, 2006): 158. http://dx.doi.org/10.1088/1367-2630/8/8/158.

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Salces-Carcoba, F., C. J. Billington, A. Putra, Y. Yue, S. Sugawa, and I. B. Spielman. "Equations of state from individual one-dimensional Bose gases." New Journal of Physics 20, no. 11 (November 23, 2018): 113032. http://dx.doi.org/10.1088/1367-2630/aaef9b.

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Hofferberth, S., I. Lesanovsky, B. Fischer, T. Schumm, and J. Schmiedmayer. "Non-equilibrium coherence dynamics in one-dimensional Bose gases." Nature 449, no. 7160 (September 2007): 324–27. http://dx.doi.org/10.1038/nature06149.

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Li, Zhi-Qiang, and Yue-Ming Wang. "One-dimensional spin-orbit coupling Bose gases with harmonic trapping." Acta Physica Sinica 68, no. 17 (2019): 173201. http://dx.doi.org/10.7498/aps.68.20190143.

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Hou, Ji-Xuan. "Microcanonical condensate fluctuations in one-dimensional weakly-interacting Bose gases." Modern Physics Letters B 34, no. 35 (August 25, 2020): 2050410. http://dx.doi.org/10.1142/s0217984920504102.

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Weakly interacting Bose gases confined in a one-dimensional harmonic trap are studied using microcanonical ensemble approaches. Combining number theory methods, I present a new approach to calculate the particle number counting statistics of the ground state occupation. The results show that the repulsive interatomic interactions increase the ground state fraction and suppresses the fluctuation of ground state at low temperature.

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Astrakharchik, G. E., D. Blume, S. Giorgini, and B. E. Granger. "Quantum Monte Carlo study of quasi-one-dimensional Bose gases." Journal of Physics B: Atomic, Molecular and Optical Physics 37, no. 7 (March 24, 2004): S205—S227. http://dx.doi.org/10.1088/0953-4075/37/7/066.

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Frantzeskakis, D. J., P. G. Kevrekidis, and N. P. Proukakis. "Crossover dark soliton dynamics in ultracold one-dimensional Bose gases." Physics Letters A 364, no. 2 (April 2007): 129–34. http://dx.doi.org/10.1016/j.physleta.2006.11.074.

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Дисертації з теми "One-Dimensional Bose Gases"

Ferreras, Jorge. "One-dimensional Bose gases on an atom chip." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53074/.

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Ultracold atomic gases have proven to be an excellent tool for research in quantum systems. A Bose gas can be trapped on an atom chip using very well defined and tunable spatially-dependent potentials. The proximity of the atoms to the chip permits the use of low currents allowing for highly accurate temporal changes. Excellent experimental apparatus is needed to achieve Bose-Einstein condensation with a sufficient atom number to study low-dimensional physics. The setup described in this document utilises a set of current-carrying structures on top of which an atom chip sits. For improved atom loading rate, a two-dimensional loading stage was added, extending the lifetime of the magnetic trap. From this loading stage to the atom chip, Bose-Einstein condensation of 105 Rubidium-87 atoms was achieved in less than 30 s, allowing for a large rate of experimental cycles. The high spatial and temporal tunability of this setup results in the ability to split the atomic cloud and quench the trapping potential geometry. Maximising the ratio between trapping frequencies for different spatial directions leads to the system presenting features of a one-dimensional gas. Manipulating the coherence dynamics of a one-dimensional Bose-Einstein condensate creates fluctuations in the phase properties of the wavefunction. These fluctuations are observed as atom density perturbations after releasing the trapping potentials, and are a tool for temperature measurements. When the cloud of atoms is positioned at a few tens of micrometres from the surface of the atom chip, corrugations in the microstructures of the chip affect the trapping potentials at very low temperatures 1 μK. This effect is simulated and quantified in the thesis, with the aim of improving future setups. Additionally, the effect is explored for microscopy purposes. The behaviour of a Bose-Einstein condensate, especially the expansion rate, has long been studied. In this thesis, the Gross-Pitaevskii Equation is introduced, finding its numerical solutions to the two-dimensional and three-dimensional forms, using the Split-Step Fourier Method. The results show very good agreement with the experimental results, as well as with other well- established theories of condensates. The creation of such a toolbox opens up the opportunity to further investigate the coherence dynamics of low-dimensional systems.

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Fersino, Enrico. "Matter-wave solitons for one-dimensional Bose gases." Doctoral thesis, SISSA, 2008. http://hdl.handle.net/20.500.11767/4182.

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Thirteen years after the first experimental observation of a Bose-Einstein condensed state (BEC) [1] in a dilute Bose gas of alkali atoms, the study of ultracold quantum systems has become a well established and active area of research in contemporary physics [2, 3] which encompasses a number of different fields like atomic, condensed matter and nuclear physics...

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Holdaway, David Ian Henry. "Many body effects in one-dimensional attractive Bose gases." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7733/.

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In this thesis we investigate the properties of ultra-cold quantum gases in reduced dimension and the effects of harmonic confinement on soliton-like properties. We study regimes of agreement between mean-field and many-body theories the generation of entanglement between initially independent finite sized atomic systems. Classical solitons are non-dispersing waves which occur in integrable systems, such as atomic Bose-Einstein condensates in one dimension. Bright and dark solitons are possible, which exist as peaks or dips in density. Quantum solitons are the bound-state solutions to a system satisfying quantum integrability, given via the Bethe Ansatz. Such integrability is broken by the introduction of harmonic confinement. We investigate the equivalence of the classical field and many-body solutions in the limit of large numbers of atoms and derive numerical and variational approaches to examine the ground state energy in harmonic confinement and the fidelity between a Hartree-product solution and a quantum soliton solution. Soliton collisions produce no entanglement between either state and result only in an asymptotic position and phase shift, however external potentials break integrability and thus give the possibility of entangling solitons. We investigate the dynamical entanglement generation between two atomic dimers in harmonic confinement via exact diagonalisation in a basis of Harmonic oscillator functions, making use of the separability of the centre-of-mass component of the Hamiltonian. We show repulsive states show complex dynamics, but with an overall tendency towards states of larger invariant correlation entropy, whereas attractive states resist entanglement unless a phase matching condition is satisfied. This phase matching condition could in theory be used to generate states with highly non-Poissonian number superpositions in atomic systems with controlled number.

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BAKHTIARI, MOHAMMAD REZA. "Quantum gases in quasi-one dimensional arrays." Doctoral thesis, Scuola Normale Superiore, 2007. http://hdl.handle.net/11384/85849.

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Zhang, Wei. "Triplet Superfluidity in Quasi-one-dimensional Conductors and Ultra-cold Fermi Gases." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14139.

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This thesis presents theoretical investigations of triplet superfluidity (triplet superconductivity) in quasi-one-dimensional organic conductors and ultra-cold Fermi gases. Triplet superfluidity is different from its s-wave singlet counterpart since the order parameter is a complex vector and the interaction between fermions is in general anisotropic. Because of these distinctions, triplet superfluids have different physical properties in comparison to the s-wave case. The author discusses in this thesis the interplay between triplet superconductivity and spin density waves in quasi-one-dimensional organic conductors, and proposes a coexistence region of the two orders. Within the coexistence region, the interaction between the two order parameters acquires a vector structure, and induces an anomalous magnetic field effect. Furthermore, the author analyzes the matter-wave interference between two p-wave Fermi condensates, and proposes a polarization effect. For a single harmonically trapped p-wave Fermi condensate, the author also shows that the expansion upon release from the trap can be anisotropic, which reflects the anisotropy of the p-wave interaction.

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Peotta, Sebastiano. "Nonequilibrium dynamics of strongly correlated one-dimensional ultracold quantum gases." Doctoral thesis, Scuola Normale Superiore, 2013. http://hdl.handle.net/11384/85863.

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In the original work of this Thesis we use Time Dependent Density Matrix Renormalization Group (TDMRG) to follow and study the unitary dynamics of 1D strongly interacting quantum systems. In the rest part we present our work on the collision of spin polarized fermionic clouds. We study spin drag e ects immediately after the collision. This work is relevant to current experiments where pure spin currents have been realized with ultracold atomic gases. Several of our predictions can be veri ed in future experiments on strongly interacting few-fermion systems. In the second part the highly imbalanced case of an impurity immersed in a bath of bosonic atoms is considered. The interaction of the impurity with the bath manifests in the mass renormalization and in the damping of the oscillations of the breathing mode of the impurity in a harmonic potential. We compare the TDMRG results with an analytically tractable model in which the bath is treated as a Luttinger liquid and pinpoint striking deviations from this picture due to the nonlinear nature of the Lieb-Liniger gas. This results are relevant to current and future experiments on impurities coupled to one-dimensional ultracold gases. Finally, we employ DMRG to study spin-orbit coupled bosons in 1D optical lattices, following recent remarkable experimental advances on arti cially engineered gauge elds and spin-orbit coupling in ultracold atoms. We concentrate in the Mott insulator region of the phase diagram of pseudospin-1/2 bosons with spin-orbit coupling and anisotropic interaction terms that fully break spin rotational symmetry.

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Johnson, Aisling. "One-dimensional Bose Gases on an Atom Chip : Correlations in Momentum Space and Theoretical Investigation of Loss-induced Cooling." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLO013/document.

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L'objet de cette thèse est l'étude théorique et expérimentale de gaz de Bose à une dimension (1D), confinés à la surface d'une micro-structure. Une part importante du travail de thèse a été la modification du montage expérimental: le système laser a été remplacé, et l'installation d'un nouvel objectif de grande ouverture numérique (0.4) a nécessité le changement du dessin de la puce ainsi que l'adaptation du système à vide. Nous avons étudié les corrélations du second ordre dans l'espace des impulsions, en appliquant une méthode qui nous permet d'enregistrer en une seule image la distribution en vitesses complète de notre gaz. Nos données explorent les différents régimes du gaz à faibles interactions, du gaz de Bose idéal au quasi-condensat. Ces mesures ont montré le phénomène de groupement bosonique dans les deux phases, tandis que le quasi-condensat comporte des corrélations négatives en dehors de la diagonale. Ces anti-corrélations sont une signature de l'absence d'ordre à longue portée en 1D. Les mesures sont en bon accord avec des calculs analytiques ainsi que des simulations numériques de type Monte Carlo Quantique. Ensuite, l'objet d'un second projet est l'étude du refroidissement de gaz 1D. Comme nos échantillons occupent seulement l'état fondamental du piège transverse, il n'est pas possible de sélectionner les atomes les plus énergiques pour évaporer le gaz de façon habituelle. Une méthode alternative, qui repose sur la perte non-sélective d'atomes, a été proposée et mise en pratique expérimentalement par des collègues. Leurs résultats sont compatibles avec des observations faites sur notre montage, très semblable au leur. Tout d'abord, nous avons aussi obtenu des température d'environ 10% de l'énergie de l'état fondamental transverse. Deuxièmement, des simulations champ classique ont montré la robustesse de l'état hors d'équilibre généré par de telles pertes: les différents modes perdent en effet de l'énergie à des taux différents. Ceci est en accord avec l'observation expérimentale suivante: selon la méthode de thermométrie utilisée, chacune explorant des excitations d'énergies différentes, les températures mesurées sont différentes. Enfin, nous relions cet état non-thermique à la nature intégrable du système considéré
We present experimental and theoretical results on ultracold one-dimensional (1D) Bose gases, trapped at the surface of a micro-structure. A large part of the doctoral work was dedicated to the upgrade of the experimental apparatus: the laser system was replaced and the installation of a new imaging objective of high numerical aperture (0.4) required the modification of the atom chip design and the vacuum system. We then probed second-order correlations in momentum space, using a focussing method which allows us to record the velocity distribution of our gas in a single shot. Our data span the weakly-interacting regime of the 1D Bose gas, going from the ideal Bose gas regime to the quasi-condensate. These measurements revealed bunching in both phases, while in the quasi-condensate off-diagonal negative correlations, a the signature of the absence of long-range order in 1D, were revealed. These experimental results agree well with analytical calculations and exact Quantum Monte Carlo simulations. A second project focussed on the cooling of such 1D gases. Since the samples lie in the ground state of the transverse trap, energy selection to carry out usual evaporative cooling is not possible. An alternative cooling scheme, based on non-selective removal of particles, was proposed and demonstrated by colleagues. These findings are compatible with observations on our setup, similar to theirs. Firstly, we also reached temperatures as low as 10% of the transverse gap in earlier experiments. Secondly, with classical field simulations we demonstrate the robustness of the non-thermal arising from these losses: different modes indeed lose energy at different rates. This agrees with the following observation: depending on the thermometry we use, each probing excitations of different energies, the measured temperatures are different, beyond experimental uncertainty. Finally, we relate this non-thermal state to the integrable nature of the 1D Bose gas

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Книги з теми "One-Dimensional Bose Gases"

Langen, Tim. Non-equilibrium Dynamics of One-Dimensional Bose Gases. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18564-4.

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Quantum gases in quasi-one-dimensional arrays. [Pisa, Italy]: Edizioni della Normale, 2007.

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Langen, Tim. Non-Equilibrium Dynamics of One-Dimensional Bose Gases. Springer, 2015.

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Langen, Tim. Non-Equilibrium Dynamics of One-Dimensional Bose Gases. Springer International Publishing AG, 2016.

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Langen, Tim. Non-equilibrium Dynamics of One-Dimensional Bose Gases. Springer, 2015.

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Rauer, Bernhard. Non-Equilibrium Dynamics Beyond Dephasing: Recurrences and Loss Induced Cooling in One-dimensional Bose Gases. Springer, 2020.

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Rauer, Bernhard. Non-Equilibrium Dynamics Beyond Dephasing: Recurrences and Loss Induced Cooling in One-dimensional Bose Gases. Springer, 2019.

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Eckle, Hans-Peter. Models of Quantum Matter. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199678839.001.0001.

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This book focuses on the theory of quantum matter, strongly interacting systems of quantum many–particle physics, particularly on their study using exactly solvable and quantum integrable models with Bethe ansatz methods. Part 1 explores the fundamental methods of statistical physics and quantum many–particle physics required for an understanding of quantum matter. It also presents a selection of the most important model systems to describe quantum matter ranging from the Hubbard model of condensed matter physics to the Rabi model of quantum optics. The remaining five parts of the book examines appropriate special cases of these models with respect to their exact solutions using Bethe ansatz methods for the ground state, finite–size, and finite temperature properties. They also demonstrate the quantum integrability of an exemplary model, the Heisenberg quantum spin chain, within the framework of the quantum inverse scattering method and through the algebraic Bethe ansatz. Further models, whose Bethe ansatz solutions are derived and examined, include the Bose and Fermi gases in one dimension, the one–dimensional Hubbard model, the Kondo model, and the quantum Tavis–Cummings model, the latter a model descendent from the Rabi model.

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Частини книг з теми "One-Dimensional Bose Gases"

Langen, Tim. "Introduction to One-Dimensional Bose Gases." In Springer Theses, 1–37. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18564-4_1.

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Bouchoule, I., N. J. van Druten, and C. I. Westbrook. "Atom Chips and One-Dimensional Bose Gases." In Atom Chips, 331–63. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527633357.ch11.

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Langen, Tim. "Experimental Realization of One-Dimensional Bose Gases." In Springer Theses, 39–65. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18564-4_2.

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Langen, Tim. "Relaxation and Prethermalization in One-Dimensional Bose Gases." In Springer Theses, 75–95. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18564-4_4.

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Langen, Tim. "Relaxation Dynamics in an Imbalanced Pair of One-Dimensional Bose Gases." In Springer Theses, 123–33. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18564-4_7.

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Pitaevskii, Lev, and Sandro Stringari. "Quantum Gases in Cigar and One-dimensional Regimes." In Bose-Einstein Condensation and Superfluidity, 482–511. Oxford University Press, 2016. http://dx.doi.org/10.1093/acprof:oso/9780198758884.003.0024.

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Eckle, Hans-Peter. "Bose Gas in One Dimension: Lieb–Liniger Model." In Models of Quantum Matter, 545–82. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199678839.003.0015.

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The coordinate Bethe ansatz can be extended to a model, the Lieb–Liniger model, of a one-dimensional gas of Bosons interacting with repulsive δ‎-function potentials. It has attracted attention due to its relevance for experimental developments in the fields of ultracold gases and optical lattices. This chapter provides an exposition of the related classical nonlinear Schrödinger equation, followed by its generalization to the quantum model. It explores a limiting case, the Tonks-Girardeau gas. The δ‎-function potentials supply a kind of boundary condition on the wave functions allowing us to analyze the eigenfunctions of the Bethe ansatz, which are examined on the infinite line and for periodic boundary conditions. The latter leads to the Bethe ansatz equations. The solution of these equations is achieved in the thermodynamic limit for the ground state and for low-lying excited states.

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Тези доповідей конференцій з теми "One-Dimensional Bose Gases"

SEIRINGER, ROBERT, ELLIOTT H. LIEB, and JAKOB YNGVASON. "One-dimensional behavior of dilute Bose gases in traps." In XIVth International Congress on Mathematical Physics. WORLD SCIENTIFIC, 2006. http://dx.doi.org/10.1142/9789812704016_0015.

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Rogel-Salazar, Jesus, and Edward A. Hinds. "Classification of quantum degenerate regimes in one-dimensional Bose gases." In International Quantum Electronics Conference. Washington, D.C.: OSA, 2004. http://dx.doi.org/10.1364/iqec.2004.itui19.

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Langen, Tim, Michael Gring, Maximilian Kuhnert, Bernhard Rauer, Remi Geiger, Igor Mazets, David Adu Smith, Takuya Kitagawa, Eugene Demler, and Jörg Schmiedmayer. "Studying non-equilibrium many-body dynamics using one-dimensional Bose gases." In INTERNATIONAL CONFERENCE ON QUANTITATIVE SCIENCES AND ITS APPLICATIONS (ICOQSIA 2014): Proceedings of the 3rd International Conference on Quantitative Sciences and Its Applications. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4903080.

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Hargather, Michael J., Joshua L. Smith, James Anderson, and Kyle Winter. "Optical Diagnostics for Energetic Materials Research." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67372.

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Optical diagnostics including schlieren, shadowgraphy, and background-oriented schlieren (BOS) are used to visualize shock waves and compressible flow phenomena present in energetic and explosive events. These techniques visualize refractive index variations to obtain a range of qualitative and quantitative information. A one-dimensional explosively-driven shock tube facility is used with schlieren imaging to measure shock wave propagation speeds from explosive-thermite mixtures. The schlieren imaging visualizes turbulent flow structures in the expanding product gas region. An imaging spectrometer is paired with the schlieren imaging to quantify the mixing of the explosive product gases with the ambient environment. Shadowgraphy is applied to image field-scale explosive tests. The shadowgraph images reveal shock waves, fragment motion and speed, and the motion of product gases. BOS is a modern technique for visualizing refractive fields via their distortion of a background pattern. Here the technique is applied to image field-scale explosive events using the ambient background of the test pad. The BOS images clearly show shock wave propagation and reflection from surfaces, which is not clearly visible in the raw high-speed digital images.

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Vieira, João Marcos Bastos, and José Renato Mendes de Sousa. "Gas Diffusion in Flexible Pipes: A Comparison Between Two- and Three-Dimensional FE Models to Predict Annulus Composition." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-78325.

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Abstract The Brazilian offshore oil and gas industry uses flexible pipes to transport water, oil, and/or gas. Currently, the high concentration of acid gases, such as carbon dioxide (CO2) and hydrogen sulfide (H2S), in Brazilian pre-salt wells has been introducing new challenges to these pipes. The acid gases may migrate from the bore to the annulus of these structures, forming a corrosive environment that can induce the steel armors’ failure by SCC (Stress Corrosion Cracking) or HIC (Hydrogen Induced Cracking). Hence, predicting the gas composition in the annulus is of fundamental importance to ensure the safe operation of flexible pipes. However, this prediction involves complex gas permeation analyses through the layers of these pipes. For instance, the permeation rate depends on temperature, gases partial pressures, and the free volume distribution. Therefore, new tools are required to understand better the fluid permeation between the flexible pipes’ layers. Therefore, this paper presents and compares two finite element (FE) models to predict the annulus composition of flexible pipes. Both models consider the temperature gradient effects on the layers’ material properties. On the one hand, the first approach deals with a two-dimensional model that considers helical layers as rings. So, the shielding effect is simplified. On the other, the second develops a complete three-dimensional model of the cross-section geometry. The results indicate that, while being faster, the two-dimensional approach shows higher concentration results than the three-dimensional approach. Furthermore, the difference between the two approaches suggests that the shielding provided by the helicoidal wires is relevant.

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Murakami, Tamotsu, and Yuki Hamasaki. "Basic Study of Autologous-Bone-Replaceable Artificial Bone Fabrication With Porosity Distribution Using Electrolysis." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28645.

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Recently, the use of bioresorbable materials (e.g., β-tricalcium phosphate (β-TCP)) has enabled the development of autologous-bone-replaceable artificial bones that are degraded and resorbed, i.e., replaced with autologous bone, when placed inside the human body for a sufficiently long duration. Although such autologous-bone replaceability requires high porosity of the artificial bone to promote the ingression of blood vessels and cells, the high porosity reduces the mechanical strength, which leads to disadvantages such as possible fracture after bone substitution surgery. One solution to this problem is to optimally arrange low-porosity portions for mechanical strength and high-porosity portions for autologous-bone replaceability in solid artificial bones. Commercially available artificial bones typically have fixed shapes such as a rectangular parallelepiped or cylinder. The use of recent solid freeform fabrication technologies, however, has enabled solid artificial bones with various shapes to be customized for individual medical cases. In this paper, the authors propose a solid freeform fabrication method for autologous-bone-replaceable artificial bones with a porosity distribution. A β-TCP porous artificial bone can be fabricated by placing a slurry consisting of β-TCP powder, water, a peptization reagent and a frother in a mold, drying it to form a solid shape and then sintering it. This β-TCP slurry contains ammonium polyacrylate as the peptization reagent, which is an electrolyte, and ammonia, hydrogen and oxygen gases are produced from its electrolysis. The authors conceived the idea of controlling the foaming of the β-TCP slurry by electrolysis, and of designing and implementing a fabrication system consisting of a fine nozzle with a microscrew for extruding β-TCP slurry as a filament and electrodes for controlling the electrolysis of the slurry. Using this system, we can fabricate a solid shape by drawing two-dimensional sections with the slurry filament and stacking each section, and at the same time vary the porosity by controlling the electric current applied for the electrolysis of the slurry. Using the experimental system, three β-TCP porous samples (approximately 18mm × 18mm × 9mm) of high (71.8%), medium (59.5%) and low (54.6%) porosity are successfully fabricated by applying electric currents of 20mA, 10mA and 0mA, respectively. Then a β-TCP porous sample (approximately 40mm × 10mm × 10mm) with a gradient porosity distribution (from 72.3% to 56.1%) is successfully fabricated by varying the electric current from 0mA to 20mA in a continuous fabrication process. From these results, the authors confirm the efficacy and potential of the proposed approach.

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Kirkpatrick, Allan, Gi-Heon Kim, and Daniel Olsen. "CFD Modeling of the Performance of a Prechamber for Use in a Large Bore Natural Gas Engine." In ASME 2005 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ices2005-1049.

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The topic of this paper is the performance of a prechamber for use in a large bore two stroke natural gas engine. With increased regulation of emissions from stationary natural gas engines, there has been interest in modification of the combustion process, such as extending the lean limit, to reduce NOx emissions. One promising combustion technique uses an ignition prechamber. CFD models of a prechamber and the cylinder were developed in order to simulate the performance of a prechamber ignition system. The modeling included a full three dimensional transient analysis with scavenging, moving piston, and main chamber fuel injection. The CFD analysis included the fuel injection into the prechamber, pressurization by the inflowing main chamber gases, spark ignition, combustion, and flame propagation into the main combustion chamber. The computations indicated that the prechamber is more well mixed than the main engine chamber, with the prechamber mixture close to stoichiometric for better ignition. There is a strong, well-organized vortex in the prechamber induced by the incoming jet from the main chamber. The combustion flame in the prechamber travels in the direction of the gas vortex along lines of increasing equivalence ratio. The flame then propagates across the main cylinder in a very uniform fashion, indicating that there is sufficient energy to ignite the lean, partially mixed mixture in the main chamber. The orientation of the prechamber nozzle was also investigated, and an orientation of twenty degrees relative to the main chamber was found to produce a flame that did not impinge on the piston.

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Theaker, M., R. Rahmani, and H. Rahnejat. "Prediction of Ring-Bore Conformance and Contact Condition and Experimental Validation." In ASME 2012 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ices2012-81021.

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One of the key conjunctions in the IC engine is that made by the top compression ring to the cylinder liner. Although the compression ring has seen considerable improvements since its introduction into steam engines by John Ramsbottom in the 1850s, its multiple and often contradictory functions still remain a challenge today. The primary aim has always been to seal the combustion chamber and guard against leakage of combustion gasses. The ring is also required to conduct some of the generated heat away. These requirements call for good ring-bore conformance, but often at the expense of increased friction. A simplified inter-ring gas flow model, as well as the measured chamber pressure using a Kistler pressure transducer is carried out under motored conditions to obtain the net gas pressure acting behind the ring. This and the elastic pressure as the result of ring restoring tension force in fitment constitute the contact load, which is usually carried by a mixed-hydrodynamic regime of lubrication. The conjunction pressures are treated as a combination of hydrodynamic generated pressures and asperity-pair interactions. The former is obtained by solution of two dimensional Reynolds equation, whilst the latter is determined assuming a Gaussian distribution of asperities on the counterfaces. Surface topography of the bounding solids; the compression ring and the liner are measured and used as appropriate statistical functions in the Greenwood and Tripp model. Using an analytical flow model, pressure acting behind the ring (on the inner periphery of the ring) is obtained, leading to the calculation of ring-bore friction. A floating liner is used to measure friction of piston and ringpack in situ. The characteristic of the predicted variations are compared with the measured data. However, a quantitative comparison is not possible as the measured data corresponds to all the conjunctions of piston system, including the oil control rings as well as the piston skirt. The results show that variation of gas force behind the ring significantly changes the ring-bore contact, thus friction and the nature of interactions.

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Ismail, Islam, Ahmed Emara, and El Sayed Abdel Razek. "Thermo Mechanical Analysis of a Direct Injection Heavy Duty Diesel Engine Piston Using FEA." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66160.

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This paper involves simulation of a 4-stroke direct injection heavy duty diesel engine piston made of aluminum silicon alloy to determine its temperature field, stress distribution and deformation at the conditions of upgrading the engine power from 300 HP to 350 HP. Turbocharger is the way used to enhance the engine power from 300 HP to 350 HP beside improving the fuel injection system. When the engine power is upgraded, high temperature and pressure will be developed because the engine will run at high loads. The piston is subjected to the coupled action of the thermal effect due to the transfer of heat from the head to the body and the mechanical effect represented by the combustion pressure and the inertial load due to the important change of direction of the piston in the cylinder bore. This results in producing stresses in the piston and if these stresses exceed the designed values, the failure of the piston is the result. Finite element analysis (FEA) is considered as one of the best numerical tools to model and analyze the physical systems. The three dimensional piston model was developed in Solid-Works and imported into ANSYS software. Finite element analysis is considered Code for preprocessing, loading and post processing. The simulation parameters used in this paper were combustion pressure, inertial effects and temperature. Diesel RK software is used to simulate the thermal analysis of engine cycle at each case of engine power 300 HP and 350 HP. Also, this model included the effect of the heat flow on the piston to overcome the whole area of the piston is used to illustrate the temperature distribution on the total area of the piston. This area divided into piston surface area and sidle area of piston which included the groves of rings (pressure and oil). The heat transfer coefficient is determined in each area of the piston according to the mechanism of heat transfer. Finally, the results of two different piston conditions are compared with each other. The highest temperature appeared at the combustion chamber side which occurred at the edges of the piston top face in direct contact with the hot gases in the radial. The piston deformation value is within a safe margin and below the gap between the piston and the cylinder bore in case of engine power of 350 HP. The highest calculated value of stresses was below the yield stress of the piston material at elevated temperatures and engine brake power of 350 HP. Hence the piston would withstand the induced stresses during work cycles.

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