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Статті в журналах з теми "Non-adiabatic state transfer":

1

Dommett, Michael, and Rachel Crespo-Otero. "Excited state proton transfer in 2′-hydroxychalcone derivatives." Physical Chemistry Chemical Physics 19, no. 3 (2017): 2409–16. http://dx.doi.org/10.1039/c6cp07541j.

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ESIPT-active solid-state emitters based on 2-hydroxychalcone are almost non-emissive in solution but emit in the deep red/NIR region when crystalline. A comprehensive theoretical investigation of the gas-phase excited state relaxation pathways in five 2-hydroxychalcone systems is presented, using a combination of static and non-adiabatic simulations.
2

ZHEN, YIN. "DYNAMIC THEORY OF ELECTRON TRANSFER PROCESS." Modern Physics Letters B 02, no. 05 (June 1988): 743–52. http://dx.doi.org/10.1142/s0217984988000448.

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Based on time-dependent Hartree-Fork approximation, we have developed a new technique for dealing with non-adiabatic electron transfer process and also obtained the formula for finding consistently the effective adiabatic parameter and the transition probability. Comparing to Landau-Zener theory our results indicate that the transition probability is greatly influenced by the coupling between the electron and the heat-bath. As the initial state of the electron is in the ground state, interaction between the electron and the heat-bath reduces the transition probability between the electron states. This can be explained that the transition probability from covalent to ionic state in a solute reaction system goes down due to the influence of the solvent. As the initial state of the electron is in the excited state, the coupling to the heat-bath acts to enhance the transition probability between the electron states. This can elucidate that desorption probability decreases in the process of the electron stimulated desorption in virtue of the heat-bath.
3

Reimers, Jeffrey R., and Noel S. Hush. "The critical role of the transition-state cusp diameter in understanding adiabatic and non-adiabatic electron transfer." Russian Journal of Electrochemistry 53, no. 9 (September 2017): 1042–53. http://dx.doi.org/10.1134/s1023193517090105.

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4

Fewell, M. P., B. W. Shore, and K. Bergmann. "Coherent Population Transfer among Three States: Full Algebraic Solutions and the Relevance of Non Adiabatic Processes to Transfer by Delayed Pulses." Australian Journal of Physics 50, no. 2 (1997): 281. http://dx.doi.org/10.1071/p96071.

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Ongoing work aimed at developing highly efficient methods of populating a chosen sublevel of an energy level highlights the need to understand off-resonant effects in coherent excitation. This motivated us to re-examine some aspects of the theory of coherent excitation in a three-state system with a view to obtaining algebraic expressions for off-resonant eigenvalues and eigenvectors. Earlier work gives simple closed-form expressions for the eigenvalues this system, expressions applying even when the system is not on two-photon resonance. We present here expressions of similar simplicity for the components of the normalised eigenvectors. The analytic properties of these components explain the observed sensitivity of the stimulated-Raman-adiabatic-passage process (STIRAP) to the condition of two-photon resonance. None of the eigenstates is ‘trapped’ or ‘dark’ unless the system is on two-photon resonance; off resonance, all states have nonzero projections on the unperturbed intermediate state. A simple argument shows that no dressed state can be adiabatically connected to both the unperturbed initial and final states when the system is off two-photon resonance. That is, adiabatic transfer from initial to final state requires that these be degenerate before and after the STIRAP pulse sequence, and this implies zero two-photon detuning. However, substantial transfer probabilities are observed experimentally for very small two-photon detunings. We show that such systems are characterised by very sharp avoided crossings of two eigenvalues, and that the observed population transfer can be understood as an effect of non adiabatic transitions occurring at the avoided crossings.
5

Chen, Wen-Kai, Ganglong Cui, and Xiang-Yang Liu. "Solvent effects on excited-state relaxation dynamics of paddle-wheel BODIPY-Hexaoxatriphenylene conjugates: Insights from non-adiabatic dynamics simulations." Chinese Journal of Chemical Physics 35, no. 1 (February 2022): 117–28. http://dx.doi.org/10.1063/1674-0068/cjcp2110214.

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Understanding the excited state dynamics of donor-acceptor (D-A) complexes is of fundamental importance both experimentally and theoretically. Herein, we have first explored the photoinduced dynamics of a recently synthesized paddle-wheel BODIPY-hexaoxatriphenylene (BODIPY is the abbreviation for BF2-chelated dipyrromethenes) conjugates D-A complexes with the combination of both electronic structure calculations and non-adiabatic dynamics simulations. On the basis of computational results, we concluded that the BODIPY-hexaoxatriphenylene (BH) conjugates will be promoted to the local excited (LE) states of the BODIPY fragments upon excitation, which is followed by the ultrafast exciton transfer from LE state to charge transfer (CT). Instead of the photoinduced electron transfer process proposed in previous experimental work, such a exciton transfer process is accompanied with the photoinduced hole transfer from BODIPY to hexaoxatriphenylene. Additionally, solvent effects are found to play an important role in the photoinduced dynamics. Specifically, the hole transfer dynamics is accelerated by the acetonitrile solvent, which can be ascribed to significant influences of the solvents on the charge transfer states, i.e. the energy gaps between LE and CT excitons are reduced greatly and the non-adiabatic couplings are increased in the meantime. Our present work not only provides valuable insights into the underlying photoinduced mechanism of BH, but also can be helpful for the future design of novel donor-acceptor conjugates with better optoelectronic performance.
6

Cina, Jeffrey A. "Dynamics of an excitation-transfer trimer: Interference, coherence, Berry’s phase development, and vibrational control of non-adiabaticity." Journal of Chemical Physics 158, no. 12 (March 28, 2023): 124307. http://dx.doi.org/10.1063/5.0139174.

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We detail several interesting features in the dynamics of an equilaterally shaped electronic excitation-transfer (EET) trimer with distance-dependent intermonomer excitation-transfer couplings. In the absence of electronic-vibrational coupling, symmetric and antisymmetric superpositions of two single-monomer excitations are shown to exhibit purely constructive, oscillatory, and purely destructive interference in the EET to the third monomer, respectively. In the former case, the transfer is modulated by motion in the symmetrical framework-expansion vibration induced by the Franck–Condon excitation. Distortions in the shape of the triangular framework degrade that coherent EET while activating excitation transfer in the latter case of an antisymmetric initial state. In its symmetrical configuration, two of the three single-exciton states of the trimer are degenerate. This degeneracy is broken by the Jahn–Teller-active framework distortions. The calculations illustrate closed, approximately circular pseudo-rotational wave-packet dynamics on both the lower and the upper adiabatic potential energy surfaces of the degenerate manifold, which lead to the acquisition after one cycle of physically meaningful geometric (Berry) phases of π. Another manifestation of Berry-phase development is seen in the evolution of the vibrational probability density of a wave packet on the lower Jahn–Teller adiabatic potential comprising a superposition of clockwise and counterclockwise circular motions. The circular pseudo-rotation on the upper cone is shown to stabilize the adiabatic electronic state against non-adiabatic internal conversion via the conical intersection, a dynamical process analogous to Slonczewski resonance. Strategies for initiating and monitoring these various dynamical processes experimentally using pre-resonant impulsive Raman excitation, short-pulse absorption, and multi-dimensional wave-packet interferometry are outlined in brief.
7

Yan, B. H., Han Yang Gu, Y. H. Yang, and L. Yu. "CFD Analysis of Turbulent Flow in Typical Rod Bundles in Rolling Motion." Applied Mechanics and Materials 29-32 (August 2010): 716–24. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.716.

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The influence mechanism of rolling motion on the flowing and heat transfer characteristics of turbulent flow in typical four rod bundles is investigated with FLUENT code. The flowing and heat transfer characteristics of turbulent flow in rod bundles can be affected by rolling motion. But the flowing similarity of turbulent flow in adiabatic and non-adiabatic can not be affected. If the rolling amplitude is big or if the rolling period is small, the radial additional force can make the parameter profiles and the turbulent flowing and heat transfer change greatly. And the frictional resistance coefficient and heat transfer coefficient can not be solved by the correlations in steady state. In rolling motion, as the pitch to diameter ratio decrease, especially if it is less than 1.1, the flowing and heat transfer of turbulent flow in rolling motion change significantly.
8

Lane-Serff, G. F., and S. D. Sandbach. "Emptying non-adiabatic filling boxes: the effects of heat transfers on the fluid dynamics of natural ventilation." Journal of Fluid Mechanics 701 (May 23, 2012): 386–406. http://dx.doi.org/10.1017/jfm.2012.164.

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AbstractA model for steady flow in a ventilated space containing a heat source is developed, taking account of the main heat transfers at the upper and lower boundaries. The space has an opening at low level, allowing cool ambient air to enter the space, and an opening near the ceiling, allowing warm air to leave the space. The flow is driven by the temperature contrast between the air inside and outside the space (natural ventilation). Conductive heat transfer through the ceiling and radiant heat transfer from the ceiling to the floor are incorporated into the model, to investigate how these heat transports affect the flow and temperature distribution within the space. In the steady state, a layer of warm air occupies the upper part of the space, with the lower part of the space filled with cooler air (although this is warmer than the ambient air when the radiant transfer from ceiling to floor is included). Suitable scales are derived for the heat transfers, so that their relative importance can be characterized. Explicit relationships are found between the height of the interface, the opening area and the relative size of the heat transfers. Increasing heat conduction leads to a lowering of the interface height, while the inclusion of the radiant transfer tends to increase the interface height. Both of these effects are relatively small, but the effect on the temperatures of the layers is significant. Conductive heat transfer through the upper boundary leads to a significant lowering of the temperature in the space as a proportion of the injected heat flux is taken out of the space by conduction rather than advection. Radiative transfer from the ceiling to floor results in the lower layer becoming warmer than the ambient air. The results of the model are compared with full-scale laboratory results and a more complex unsteady model, and are shown to give results that are much more accurate than models which ignore the heat transfers.
9

Schumer, A., Y. G. N. Liu, J. Leshin, L. Ding, Y. Alahmadi, A. U. Hassan, H. Nasari, et al. "Topological modes in a laser cavity through exceptional state transfer." Science 375, no. 6583 (February 25, 2022): 884–88. http://dx.doi.org/10.1126/science.abl6571.

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Shaping the light emission characteristics of laser systems is of great importance in various areas of science and technology. In a typical lasing arrangement, the transverse spatial profile of a laser mode tends to remain self-similar throughout the entire cavity. Going beyond this paradigm, we demonstrate here how to shape a spatially evolving mode such that it faithfully settles into a pair of bi-orthogonal states at the two opposing facets of a laser cavity. This was achieved by purposely designing a structure that allows the lasing mode to encircle a non-Hermitian exceptional point while deliberately avoiding non-adiabatic jumps. The resulting state transfer reflects the unique topology of the associated Riemann surfaces associated with this singularity. Our approach provides a route to developing versatile mode-selective active devices and sheds light on the interesting topological features of exceptional points.
10

Fernandez-Alberti, Sebastian, Dmitry V. Makhov, Sergei Tretiak, and Dmitrii V. Shalashilin. "Non-adiabatic excited state molecular dynamics of phenylene ethynylene dendrimer using a multiconfigurational Ehrenfest approach." Physical Chemistry Chemical Physics 18, no. 15 (2016): 10028–40. http://dx.doi.org/10.1039/c5cp07332d.

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Photoinduced dynamics of electronic and vibrational unidirectional energy transfer between meta-linked building blocks in a phenylene ethynylene dendrimer is simulated using a multiconfigurational Ehrenfest in time-dependent diabatic basis (MCE-TDDB) method.

Дисертації з теми "Non-adiabatic state transfer":

1

Ortiz, Sánchez Juan Manuel. "Excited state intramolecular proton transfer reactions coupled with non adiabatic processes: electronic structure and quantum dynamical approaches." Doctoral thesis, Universitat Autònoma de Barcelona, 2009. http://hdl.handle.net/10803/3311.

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Els enllaços d'hidrogen són d'importància universal en química i bioquímica. Les propietats dels enllaços d'hidrogen en l'estat electrònic fonamental han estat estudiades durant molt anys. Malgrat tot, molt poc es coneix sobre les reaccions químiques on intervenen enllaços d'hidrogen en els estats electrònics excitats. Una de les reaccions més interessants són les transferències protòniques intramoleculars en estat excitat (ESIPT de les seves sigles en anglès), ja que juguen un paper crucial en una gran varietat de reaccions químiques fotoquímiques de gran rellevància.
Les tècniques més modernes de cinètica química disponibles avui dia, permeten la monitorització dels processos ESIPT fins l'escala de temps del femtosegond. Tot i això, els resultats experimentals acostumen a ser difícils d'interpretar, especialment quan es veuen involucrats processos competitius. Aquests processos addicionals suposen un desafiament extra en l'estudi d'aquestes reaccions. En aquest sentit, la química teòrica i computacional representa una molt versàtil eina de treball, donat l'absolut control que els investigadors poden imposar a sistemes modelitzats aïllats.
Els sistemes moleculars recollits en la present tesi representen exemples directes dels diferents ordres de complexitat que l'estudi teòric (des del punt de vista del càlcul electrònic i dinàmic) del processos ESIPT poden representar: des de la comprensió del aspectes fonamentals del procés, fins a la necessitat d'adoptar estratègies teòriques eficients per tractar la presència de processos no adiabàtics.
Hydrogen Bonds are of universal importance in chemistry and biochemistry. The properties of hydrogen bonds in the electronic ground state have been investigated since long ago. Nevertheless, much less is known about the chemical reactions involving hydrogen bonds in excited electronic states. One of the most interesting reactions are the excited state intramolecular proton transfer (ESIPT) processes, as they play a crucial role in a plethora of photochemical reactions of chemical and biochemical relevance.
The most modern kinetic experimental techniques available today, allow the monitoring of ESIPT processes up to the order of the femtosecond. However, the experimental results are usually difficult to analyze, specially when competitive processes are involved. Those additional processes suppose an extra challenge in the study of this topic. In this sense, theoretical and computational chemistry represents a powerful tool of interpretation, given the absolute control that researchers can impose on modelized isolated systems.
The molecular systems collected in the present thesis represent direct examples of the different orders of complexity that the theoretical study (both from the electronic and dynamical points of view) of ESIPT can represent: from the comprehension of the essentials of the process, to the need of adoption of efficient theoretical strategies to treat the presence of non adiabatic processes.
2

Morrison, Adrian Franklin. "An Efficient Method for Computing Excited State Properties of Extended Molecular Aggregates Based on an Ab-Initio Exciton Model." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1509730158943602.

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3

Kiorpelidis, Ioannis-Markos. "Wave phenomena in one-dimensional space or time varying media." Electronic Thesis or Diss., Le Mans, 2023. https://cyberdoc-int.univ-lemans.fr/Theses/2023/2023LEMA1032.pdf.

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L'interaction des ondes avec des milieux possédant des fluctuations spatiales et/ou temporelles conduit à une phénoménologie intéressante. Dans ce cadre, dans la présente thèse quatre phénomènes ondulatoires sont étudiés: deux se produisant dans des milieux variant dans l’espace et deux dans des milieux variant dans le temps. Nous commençons par explorer la diffusion des ondes par une configuration spatialement périodique finie sujette à des perturbations. Nous nous concentrons sur les résonances de transmission parfaite (PTR) et nous développons une méthode pour les préserver sous des perturbations asymétriques. L'analyse effectuée révèle une connexion par paire entre les PTR d'une configuration de diffusion spatialement périodique avec des cellules à symétrie miroir. Dans le même contexte de milieux variant spatialement, nous calculons la longueur de localisation des modes de bord topologiques qui sont supportés dans une chaîne mécanique masse-ressort possédant des fluctuations aléatoires de ses paramètres de rigidité. En présence d'un fort désordre chiral, la longueur de localisation diverge, ce qui implique une transition de phase topologique induite uniquement par le désordre. Dans une prochaine étape, nous considérons le cas où les couplages de la chaîne masse-ressort mécanique varient avec le temps de manière déterministe. Ce système variable dans le temps peut alors servir de plate-forme pour transférer un mode de bord topologique. Au-delà de la limite adiabatique, nous concevons un protocole pour les couplages variables dans le temps qui aboutit à un transfert rapide et robuste et conduit encore plus à une amplification du mode de bord transféré. Pour éclairer le phénomène d'amplification dans une plateforme variable dans le temps, nous explorons la propagation d'une onde dans un milieu à indice de réfraction périodique et dont la dynamique des ondes est régie par l'équation de Mathieu. L'onde présente une amplification transitoire en raison de la nature non normale de la matrice de propagation et nous fournissons la preuve numérique que les caractéristiques d'amplification globales sont fournies simplement par la matrice de monodromie
The interaction of waves with media possessing spatial or/and temporal fluctuations leads tointeresting phenomenology. Within this framework, in the present thesis four wave phenomena arestudied: two occurring in spatially-varying media and two in time-varying media. We begin byexploring wave scattering by a finite spatially-periodic setup that is subject to perturbation. Ourfocus is on perfect transmission resonances (PTRs) and we develop a method for preserving themunder asymmetric perturbations. The performed analysis reveals a pairwise connection betweenPTRs of a spatially-periodic scattering setup with mirror symmetric cells. In the same contextof spatially varying media, we compute the localization length of the topological edge modes thatare supported in a mechanical mass-spring chain possessing random fluctuations of its stiffnessparameters. In the presence of strong chiral disorder the localization length diverges, implying atopological phase transition that is induced purely by disorder. As a next step we consider thecase where the couplings of the mechanical mass-spring chain vary with time in a deterministicway. Then this time-varying system can serve as a platform for transferring a topological edgemode. Going beyond the adiabatic limit, we design a protocol for the time-varying couplingsthat results in a fast and robust transfer and even more leads to amplification of the transferrededge mode. To shed light into the phenomenon of amplification in a time-varying platform, weexplore the propagation of a wave in a medium with time-periodic refractive index and with wavedynamics governed by the Mathieu equation. The wave exhibits transient amplification due to thenon normal nature of the propagator matrix and we provide numerical evidence that the globalamplifying features are provided merely by the monodromy matrix
4

Ho, Emmeline. "Vers un modèle vibronique innovant pour les hydrocarbures conjugués." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS087/document.

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Cette thèse s'intéresse à la rationalisation du mécanisme de transfert d'excitation dans des polyphénylènes éthynylènes (PPE). Une étude statique approfondie a été réalisée en utilisant la TDDFT, permettant de confirmer la localisation des états excités de méta-PPE sur des fragments para, ainsi que la hiérarchie des interactions régissant les propriétés photochimiques des PPE. Des intersections coniques ont été identifiées, de même que les principales composantes de l'espace de branchement. Leur étude a soutenu l'hypothèse d'un transfert d'énergie par conversion interne entre états excités localisés sur des fragments para.D'autre part, nous avons proposé un modèle vibronique multiéchelles pour l'énergie des états électroniques. En particulier, nous avons exprimé les énergies des orbitales frontières de PPE en fonction des énergies des orbitales frontières du benzène et de l'acetylène via un Hamiltonien effectif de type Hückel. Un travail de mapping et d'optimisation nous a permis d'aboutir à une expression pour l'énergie de transition électronique en fonction d'un nombre réduit de coordonnées nucléaires locales
The present work is focused on the rationalization of the excitation transfer mechanism in polyphenylene ethynylenes (PPEs). A static study was performed using TDDFT, allowing to confirm both the localization of the excited states of meta-PPEs on para building blocks and the hierarchy in the interactions governing the photochemical properties of PPEs. Conical intersections were identified, along with few components of their branching spaces. Studying those supported the assumption of an energy transfer proceeding through internal conversion between excited states localized on different building blocks.In addition, we proposed a multiscale vibronic model for the energy of the eletronic states. In particular, we expressed the energies of the frontier orbitals of PPEs in terms of the energies of the frontier orbitals of benzene and acetylene, using an effective Hückel-type Hamiltonian. Perfoming different optimizations, we achieved to propose an expression for the energy of the electronic transition in terms of a reduced number of local nuclear coordinates
5

Posenitskiy, Evgeny. "Dynamique moléculaire non-adiabatique des complexes de type PAH." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30080.

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Les hydrocarbures aromatiques polycycliques (PAH) ont été proposés comme porteurs principaux de bandes interstellaires diffuses observées dans le milieu interstellaire, motivant des études approfondies de leur réponse photophysique et photochimique au rayonnement UV. Les mécanismes sous-jacents en compétition déterminent l'évolution du gaz dans le milieu interstellaire. L'objectif principal de cette thèse est de décrire et de comprendre les mécanismes de relaxation dans des PAHs de grande taille, par des simulations de dynamique moléculaire non-adiabatique, couplées à l'approche de la réponse linéaire "Time-Dependent Density Functional based Tight Binding" (TD-DFTB) des états excités. Des développements substantiels, prérequis ont été effectués dans le code DFTB deMon-Nano (http://demon-nano.ups-tlse.fr), d'abord avec le calcul des gradients analytiques des surfaces d'énergie potentielle (PES) et des couplages non-adiabatiques des états TD-DFTB. Puis, l'algorithme de trajectoire à sauts de surface minimaux (FSSH) de Tully a été adapté à l'approche TD-DFTB afin de prendre en compte les effets non-adiabatiques. Après comparaison avec des méthodes de structure électronique de référence, la première application est dédiée à la dynamique non-adiabatique de PAHs cata-condensés linéairement. La relaxation électronique de l'état excité le plus brillant a été simulée pour des polyacènes neutres constitués de 2 à 7 cycles aromatiques. Les résultats montrent une alternance marquée dans les temps de dépopulation de l'état initial pour les polyacènes contenant jusqu'à 6 cycles aromatiques, ce qui est corrélé avec une alternance des écarts d'énergie entre l'état initial et l'état situé juste dessous. Puis, l'influence de la géométrie sur la relaxation a été étudiée en comparant deux isomères, le chrysène de type "armchair-edge" et le tétracène de type "zigzag-edge". Après évaluation des paramétrages DFTB, la relaxation électronique à partir de l'état excité le plus brillant, situé autour de 270 nm pour les deux isomères, à été analysée. Les résultats montrent que la population électronique excitée du chrysène décroît un ordre de grandeur plus rapidement que celle du tétracène. Ceci est aussi corrélé à une différence significative des écarts d'énergie entre l'état initial et l'état situé juste dessous. Un dernier développement majeur concerne l'utilisation d'algorithmes "Machine Learning" (ML) proposés comme un moyen d'éviter la plupart des calculs de structure électronique, très coûteux en temps calcul. Les performances d'algorithmes de réseaux de neurones appliqués à la dynamique des états excités ont été évaluées. Le cas de la relaxation électronique dans le phénanthrène neutre a été choisi comme test en raison de divers résultats expérimentaux disponibles. L'apprentissage de plusieurs réseaux de neurones a été effectué et leurs précision et efficacité analysés. De plus, des approximations de trajectoires à sauts de surface ont été interfacées à l'approche ML, résultant en un coût négligeable des simulations de dynamique non-adiabatique. L'efficacité des diverses approches simplifiées a été comparée à FSSH. Dans l'ensemble, ML se révèle un outil très prometteur pour la dynamique dans les états excités à l'échelle de la nanoseconde. Ce travail de thèse ouvre de nouvelles voies pour étudier la photophysique théorique de complexes moléculaires de grande taille. Enfin, les outils développés et implémentés dans deMon-Nano, de manière modulaire, peuvent être combinés avec d'autres approches DFTB sophistiquées (tel que "Configuration Interaction") plus adaptées aux états à transfert de charge
Polycyclic Aromatic Hydrocarbons (PAHs) have been proposed as main carriers of diffuse interstellar bands that are observed in the interstellar medium. This has motivated an extensive study of their photophysical and photochemical response to UV irradiation. Underlying competing mechanisms drive the evolution of gas in the interstellar medium. The main objective of this thesis is to describe and to get theoretical insight in the energy relaxation mechanisms in large PAH molecules via extensive non-adiabatic molecular dynamics simulations coupled to the linear response Time-Dependent Density Functional based Tight Binding (TD-DFTB) approach of the excited states. Prerequisite substantial development was made in the DFTB deMon-Nano package (http://demon-nano.ups-tlse.fr), firstly with the implementation of analytical gradients of potential energy surfaces (PESs) and of non-adiabatic couplings within the TD-DFTB scheme. Next, the Tully's fewest-switches trajectory surface hopping (FSSH) algorithm has been adapted and coupled to the TD-DFTB scheme in order to take into account non-adiabatic transitions. After detailed methodological considerations and comparison with higher-level electronic structure methods, the first full-scale application is dedicated to non-adiabatic molecular dynamics of linearly cata-condensed PAHs. Electronic relaxation from the brightest excited state has been simulated for neutral polyacenes with 2 to 7 aromatic cycles. The results display a striking alternation in decay times of the brightest singlet state computed for polyacenes with up to 6 aromatic cycles, which is correlated with a qualitatively similar alternation of energy gaps between the brightest state and the state lying just below in energy. Next, the influence of geometry on relaxation has been investigated through the comparison of two isomers: armchair-edge chrysene versus zigzag-edge tetracene. After assessing the performance of DFTB parameter sets, the main focus is given to the analysis of the electronic relaxation from the brightest excited state, which is located around 270 nm for both isomers. The results show that the electronic population of the brightest excited state in chrysene decays an order-of-magnitude faster than that in tetracene. This is correlated with a significant difference in energy gaps between the brightest state and the state lying just below in energy, which is consistent with the previous conclusions for polyacenes. A last major development concerns the use of Machine Learning (ML) algorithms that have been proposed as a way to avoid most of the computationally-demanding electronic structure calculations. It aims to assess the performance of neural networks algorithms applied to excited-state dynamics. Electronic relaxation in neutral phenanthrene has been chosen as a test case due to the diversity of available experimental results. Several neural networks have been trained with different parameters and their respective accuracy and efficiency analyzed. In addition, approximate trajectory surface hopping schemes have been interfaced to ML-based PESs and gradients, resulting in non-adiabatic dynamics simulations at a negligible cost. Various simplified hopping approaches have been compared with FSSH. Overall, ML is found to be a highly promising tool for nanosecond-long molecular dynamics in excited states. This PhD research opens new avenues to investigate theoretical photophysics of large molecular complexes. Last but not least, the theoretical tools developed and implemented in deMon-Nano in a modular way can be further combined with other advanced (such as Configuration Interaction) DFTB techniques better adapted to charge-transfer states

Частини книг з теми "Non-adiabatic state transfer":

1

Carrington, Gerald. "The second law." In Basic Thermodynamics, 102–29. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198517481.003.0006.

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Abstract We showed that the integral is independent of the path of integration provided the process is quasistatic and we found that the entropy has some interesting properties: It is useful for representing adiabatic quasistatic processes, S being constant. S always increases in an adiabatic non-quasistatic process (Section 4.2). When an isolated system is allowed to change state, as in heat transfer between two bodies, the equilibrium state is associated with the state of maximum entropy (Section 4.2). The ideal gas Carnot cycle takes on a simple rectangular shape in (T, S) coordinates (Section 4.3).
2

NOURTIER, ALAIN. "BOUND STATES, RESONANCES AND THEORY OF NON-ADIABATIC CHARGE TRANSFER." In Electronic Processes at Solid Surfaces, 85–106. WORLD SCIENTIFIC, 1996. http://dx.doi.org/10.1142/9789812831552_0004.

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3

"More complex systems." In The Quantum Classical Theory, edited by Gert D. Billing. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195146196.003.0009.

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By more complex systems we mean systems containing on the order of hundreds or thousands of atoms, or molecules with less atoms but with “complicated” motions, the latter being the case when considering collisions between polyatomic molecules. In the present chapter we deal with quantum-classical methods for treating energy transfer in collisions involving polyatomic molecules, molecule surface scattering, reactions in polyatomic systems and solution. We will assume that it is possible to construct realistical potential energy surfaces for the systems. Obviously, these surfaces will be of empirical or semi-empirical nature. In some of the methods, as for instance the reaction path method, one tries to minimize the information needed on potential energy surfaces. Chemical reactions and energy transfer processes in the gas phase are often studied using just a single adiabatic Born-Oppenheimer potential energy surface. However non-adiabatic effects, that is, coupling between different electronic states, is an important aspect in chemistry. If the coupling between the various electronic states can be neglected, the “electronic” effect reduces to that of a statistical degeneracy factor ge [180].

Тези доповідей конференцій з теми "Non-adiabatic state transfer":

1

O’Dowd, Devin, Qiang Zhang, Phil Ligrani, Li He, and Stefan Friedrichs. "Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59376.

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The present study considers spatially-resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Six different measurement and processing techniques are considered and compared, including transient infrared thermography and thin-film heat flux gauges. Three methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. The three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1-D non-steady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. A fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady state condition using a thin-foil heater on the tip surface. The fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady state condition is present. Finally, the sixth method employs thin-film gauges to measure surface temperature histories at four discreet blade tip locations. With this approach, heat flux reconstruction is used to calculate the transient heat transfer coefficients and adiabatic wall temperatures. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the Impulse method, is the most accurate and reliable method to obtain detailed, spatially-resolved heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade.
2

Speetjens, M. F. M. "Chaotic Mixing: A Sure Way for Optimal Thermal Conditions?" In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22797.

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Chaotic fluid mixing is generally considered to enhance fluid-wall heat transfer and thermal homogenisation in laminar flows. However, this essentially concerns the transient stage towards a fully-developed (thermally-homogeneous) asymptotic state and then specifically for high Pe´clet numbers Pe (convective heat transfer dominates). The role of chaos in the asymptotic state at lower Pe, relevant to continuously-operating compact devices as, for instance, micro-electronics cooling systems, remains largely unexplored to date. The present study seeks to gain first insight into this matter by the analysis of a representative model problem: heat transfer in the 2D time-periodic lid-driven cavity flow induced via non-adiabatic walls. The asymptotic time-periodic thermal state is investigated in terms of both the temperature field and the thermal transport routes. This combined Eulerian-Lagrangian approach enables fundamental investigation of the connection between heat transfer and chaotic mixing and its ramifications for temperature distributions and heat-transfer rates. The analysis exposes a very different role of chaos in that its effectiveness for thermal homogenisation and heat-transfer enhancement is in low-Pe asymptotic states marginal at best. Here chaos may in fact locally amplify temperature fluctuations and thus hamper instead of promote thermal homogeneity. These findings reveal that optimal thermal conditions are not always automatic with chaotic mixing and may depend on a more delicate interplay between flow and heat-transfer mechanisms.
3

Abuaf, N., R. Bunker, and C. P. Lee. "Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-003.

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A warm (315 C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature-time variations and of the film effectiveness from the steady wall temperatures within the same aero-thermal environment. The linear cascade consists of five airfoils. The 14% cascade inlet free stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20% axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.
4

Okada, Tadashi, Shinya Nishikawa, Kenji Kanaji, and Noboru Mataga. "Dynamics of Intramolecular Electron Transfer in Polar Solvents." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/up.1990.thb5.

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When the electronic interaction between an electron donor (D) and acceptor (A) is very weak, the electron transfer (ET) process is considered to be non-adiabatic. When the interaction become fairly strong, the reaction will become adiabatic. If the electronic interaction becomes sufficiently strong and the energy gap relations are also favorable, the ET process will become barrierless. In such case it is believed that the ET process is governed mainly by the orientational motions of polar solvent molecules or polar groups in the environment surrounding D and A, and the longitudinal dielectric relaxation time τL will be important as a factor controlling the ET rate. In a limit of strong interaction between D and A groups combined by rigid spacer or single bond, its excited singlet state can be regarded as a very polar single molecule and we can observe a large fluorescence Stokes shift due to the solution in polar solvents. For the elucidation of the above mechanisms, especially the interaction of D and A with solvent including its dynamical effects on the ET process, systematic femtosecond-picosecond laser photolysis studies on various combined D, A system with different degrees of electronic interaction between them are of crucial importance.
5

Ding, Shuiting, Hang Yu, Tian Qiu, and Chuankai Liu. "Modeling of the Cavity Response to Rapid Transient Considering the Effect of Heat Transfer." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75264.

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The internal air system, as one of the important subsystems of the aeroengine, is used to cooling and sealing, and plays a vital role in the safe operation of the engine. Especially in rapid transients, the complex dynamic response in air system may impose hazardous transition state loads on engine. Cavity is a component with pretty evident characteristics of transient in the air system due to the storage and release effects on the air. The flow and heat transfer characteristics of cavity should be made clear to precisely quantify the performance of the air system. The traditional study on cavity is based on the adiabatic assumption. However, the assumption is applicable to the transient of millisecond time scales physical phenomena in the air system, which is not usually common. Generally, the actual transition process is not instantaneous. Great discrepancies exist in the process of transition predicted by the adiabatic hypothesis compared with the practical process. The objective of this work is to propose a feasible method to solve the heat transfer issue throughout the transient process, which has not been settled by a proper method before, and develop a model for simulating the transient responses of the cavity with consideration of the heat transfer effect on the basis of the method. The model can predict transient responses under different thermal boundary conditions. Experiments have been developed for investigation of the charging process of the cavity. The thermal boundary can be controlled in the experiment, and the pressure and temperature responses of the cavity under different thermal boundary conditions have been analyzed. The non-dimensional numbers related to heat transfer characteristics were deduced by dimensional analysis, and the empirical formula of characteristics was proposed based on the experimental results. The non-adiabatic low-dimensional transient model of the cavity was established based on the heat transfer characteristics correlation. Results of transient responses calculated by non-adiabatic model were compared with the experimental data. It is found that both the transient responses of pressure and temperature agree well, with the maximum relative errors less than 2%. By comparison, the relative errors of pressure and temperature calculated by adiabatic model are about 8% and 12%, respectively. Meanwhile, the tendency of temperature response deviates from the actual process. Thus, the modeling method proposed is feasible and high-precision. The present work provides a technical method for establishing a low-dimensional model to describe the transient responses of the cavity with high accuracy, and supports the component-level modeling of the transient air system.
6

Van Treuren, Kenneth W., Zoulan Wang, Peter Ireland, Terry V. Jones, and S. T. Kohler. "The Role of the Impingement Plate in Array Heat Transfer." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-162.

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Most research involving arrays of impinging jets was conducted using steady state techniques which allow the impingement plate (through which the gas flows) to achieve an equilibrium (adiabatic) temperature during the test. Invariably, the impingement plate temperature was not reported for these tests as the floating temperature condition was taken to be representative of conditions in the application being modeled. Thermal analysis of gas turbine conditions showed the present authors that conditions in the engine could often be significantly different from this floating plate temperature state. Such conditions include engine operating point transients and situations in which the plate is fixed to the aerofoil in such a way to achieve good thermal contact. Furthermore, the capacity of the impingement plate to contribute to enhanced heat transfer by paying attention to the thermal boundary conditions at its support has not been realized. The influence of the impingement plate temperature on local target surface heat transfer was fully quantified by Van Treuren et al. (1993, 1994 and 1996), using a transient liquid crystal heat transfer technique. Superposition was used to show that the target surface heat flux can be written as the summation af two separate heat transfer coefficients. These temperature difference products quantify the contributions of the impingement plate and the target surface thermal boundary conditions. In other words:(1)q=hjTw-Tj+hpTw-TpVan Treuren et al.’s experiments showed the heat transfer coefficient for target surface heat flux and impingement plate to target surface temperature difference, hp, can be up to 40% of the heat transfer coefficient for plenum to target surface temperature difference, hj, in crossflow areas away from the jet stagnation zone. The present report covers steady state experiments conducted at three average jet Reynolds numbers (10,000, 14,000, and 18,000) and two impingement to target plate spacings (1 and 4) for an inline array of jets. The purpose of the experiments was to determine the adiabatic impingement plate temperature expressed as a non-dimensional temperature difference, θ. The data allow the difference in thermal boundary conditions between the steady state experiments and the transient heat transfer experiments to be accounted for.
7

Lavagnoli, S., C. De Maesschalck, and G. Paniagua. "Analysis of the Heat Transfer Driving Parameters in Tight Rotor Blade Tip Clearances." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25291.

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Turbine rotor tips and casings are vulnerable to mechanical failures due to the extreme thermal loads they undergo during engine operation. In addition to the heat flux variations during the transient phase, high-frequency unsteadiness occurs at every rotor passage, with amplitude dependent on the tip gap. The development of appropriate predictive tools and cooling schemes requires the precise understanding of the heat transfer mechanisms. The present paper analyzes the nature of the overtip flow in transonic turbine rotors running at tight clearances, and explores a methodology to determine the relevant flow parameters that model the heat transfer. Steady-state three-dimensional Reynolds-Averaged Navier-Stokes calculations were performed to simulate engine-like conditions considering two rotor tip gaps, 0.1% and 1% of the blade span. At tight tip clearance, the adiabatic wall temperature is not anymore independent of the solid thermal boundary conditions. The adiabatic wall temperature predicted with the linear Newton’s cooling law was observed to rise to non-physical levels in certain regions within the rotor tip gap, resulting in unreliable convective heat transfer coefficients. This paper investigates different approaches to estimate the relevant flow parameters that drive the heat transfer. The present study allows experimentalists to retrieve information on the gap flow temperature and convective heat transfer coefficient based on the use of wall heat flux measurements. Such approach is required to improve the accuracy in the evaluation of the heat transfer data while enhancing the understanding of tight-clearance overtip flows.
8

Speetjens, M. F. M. "The Effect of Chaotic Mixing on Heat Transfer in Continuous Thermal Processes at Low Peclet Numbers." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30797.

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Chaotic fluid mixing is generally considered to enhance fluid-wall heat transfer and thermal homogenisation in laminar flows. However, this essentially concerns the transient stage towards a fully-developed (thermally-homogeneous) asymptotic state and then specifically for high Pe´clet numbers numbers Pe (convective heat transfer dominates). The role of chaos at lower Pe under both transient and asymptotic conditions, relevant to continuous thermal processes as e.g. micro-electronics cooling, remains largely unexplored to date. The present study seeks to gain first insight into this matter by the analysis of a representative model problem: heat transfer in the 2D time-periodic lid-driven cavity flow induced via non-adiabatic walls. Transient and asymptotic states are investigated in terms of both the temperature field and the thermal transport routes. This combined Eulerian-Lagrangian approach enables fundamental investigation of the connection between heat transfer and chaotic mixing and its ramifications for temperature distributions and heat-transfer rates. The analysis exposes a very different role of chaos in that its effectiveness for thermal homogenisation and heat-transfer enhancement is in low-Pe transient and asymptotic states marginal at best. Here chaos may in fact locally amplify temperature fluctuations and thus hamper instead of promote thermal homogeneity. These findings reveal that optimal thermal conditions are at lower Pe not automatic with chaotic mixing and may depend on a delicate interplay between flow and heat-transfer mechanisms.
9

Oumechouk, Hicham T., and Mohand A. Ait-Ali. "A Steady State, Adiabatic Compression and One-Dimensional Generalized Flow Analysis of a Natural Gas Pipeline Using Soave-Redlich-Kwong Equation of State." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16460.

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Steady state adiabatic compression and one-dimensional generalized gas flow is analyzed using governing conservation laws and Redlich-Kwong-Soave (R-K-S) equation of state applied to a representative mixture of natural gas. The objective of this work is to obtain the state properties of the natural gas considered as an open thermodynamic system at compressor and gas pipeline exits, then the compressor power and energy auto-consumptions for a few diameters and pipe line lengths configurations. The adiabatic, irreversible compression process is analyzed with formal state property definitions where departures from ideal gas properties are obtained using R-K-S equation of state. The one-dimensional generalized gas flow problem is analyzed with continuity, momentum and energy equations, combined with the equation of state; Reynolds analogy between heat transfer and flow friction is adopted. This problem is thus defined with four non linear coupled differential equations; the variables to be determined are pressure, temperature, specific volume and velocity at the gas pipeline exit. The adopted calculation procedure to obtain the gas properties is iterative. It assumes pressure and temperature initial values, solves the equation of state for the specific volume and the continuity equation for the velocity, then corrects for pressure and temperature with integrated values to be used with the next iteration from a solution of the differential equations of motion and energy. This procedure is applied to a few gas pipeline configurations of pipe diameters sections and number of boosting compressor stations for a gas pipeline capacity of 13.5 billions standard cubic meters per year to be delivered to a natural gas liquefaction plant located at a sea port at a distance of some 350 miles.
10

Atkins, N. R., R. W. Ainsworth, and N. W. Harvey. "Aerodynamic Performance Measurement in a Fully Scaled Transient Turbine Test Facility." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27142.

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The practical performance, both the efficiency and durability, of a High-Pressure (HP) turbine depends on many interrelated factors, including both the steady and unsteady aerodynamics and the heat transfer characteristics. The aerodynamic performance of new turbine designs has traditionally been tested in large scale steady flow rigs, but the testing is adiabatic, and the measurement of heat transfer is very difficult. This paper presents the results of turbine aerodynamic performance measurements at the Oxford Rotor Facility (ORF). Transient test facilities such as the Oxford Rotor allow the simultaneous study of turbine performance and heat transfer. The transient operation gives engine representative Mach number, Reynolds number and gas-to-wall temperature ratios, which are key to the aerothermodynamics of a highly-loaded, transonic, HP turbine stage. Time resolved experimental results are presented together with numerical CFD predictions over a 3% range of non-dimensional speed. The precision uncertainty of the measurements has been resolved to a level comparable with the state of the art in steady flow testing, in the region of ±0.3%.

Звіти організацій з теми "Non-adiabatic state transfer":

1

Olsen, Daniel, and Azer Yalin. L52360 NOx Reduction Through Improved Precombustion Chamber Design. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), December 2018. http://dx.doi.org/10.55274/r0011536.

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several objectives were Several objectives were completed. First, a literature review was performed to assess the current technological state of prechambers. This includes state of the art design, reliability surveys, and proven prechamber design criteria. This is an enabling tool for developing new prechamber concepts for year 2 of the project. The prioritized concepts are (in order): - Improved prechamber geometry - apply high speed engine prechamber design and scale up for large bore engines. - Adiabatic prechamber - traditional prechamber will ceramic lining to reduce heat transfer to the prechamber cooling jacket - Natural Gas Reforming - reform prechamber natural gas (roughly 3% of total engine fueling) into CO and hydrogen for low emission, high flame speed ignition. - Micro Prechamber Geometry - non-fueled and fueled micro prechambers for igniting lean engine mixtures with low NOx contribution on engine out emissions (2 concepts). - Develop diagnostic tools to evaluate the performance of prechamber concepts. The tools developed were combustion visualization utilizing high speed cameras, heat release analysis, and spectroscopy.
2

Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, January 2022. http://dx.doi.org/10.54337/aau467469997.

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Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.

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