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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.
Анотація:
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.
Анотація:
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.
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.
Анотація:
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.
Анотація:
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.
Анотація:
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.
Анотація:
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.
Анотація:
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.
Анотація:
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.
Анотація:
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.
11
Abuaf, N., R. Bunker, and C. P. Lee. "Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade." Journal of Turbomachinery 119, no. 2 (April 1, 1997): 302–9. http://dx.doi.org/10.1115/1.2841113.
Анотація:
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 aerothermal environment. The linear cascade consists of five airfoils. The 14 percent 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 percent 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.
12
Szabla, Rafał, Robert W. Góra, Mikołaj Janicki, and Jiří Šponer. "Photorelaxation of imidazole and adenine via electron-driven proton transfer along H2O wires." Faraday Discussions 195 (2016): 237–51. http://dx.doi.org/10.1039/c6fd00131a.
Анотація:
Photochemically created πσ* states were classified among the most prominent factors determining the ultrafast radiationless deactivation and photostability of many biomolecular building blocks. In the past two decades, the gas phase photochemistry of πσ* excitations was extensively investigated and was attributed to N–H and O–H bond fission processes. However, complete understanding of the complex photorelaxation pathways of πσ* states in the aqueous environment was very challenging, owing to the direct participation of solvent molecules in the excited-state deactivation. Here, we present non-adiabatic molecular dynamics simulations and potential energy surface calculations of the photoexcited imidazole–(H2O)5 cluster using the algebraic diagrammatic construction method to the second-order [ADC(2)]. We show that electron driven proton transfer (EDPT) along a wire of at least two water molecules may lead to the formation of a πσ*/S0 state crossing, similarly to what we suggested for 2-aminooxazole. We expand on our previous findings by direct comparison of the imidazole–(H2O)5 cluster to non-adiabatic molecular dynamics simulations of imidazole in the gas phase, which reveal that the presence of water molecules extends the overall excited-state lifetime of the chromophore. To embed the results in a biological context, we provide calculations of potential energy surface cuts for the analogous photorelaxation mechanism present in adenine, which contains an imidazole ring in its structure.
13
Jankowska, Joanna, Mario Barbatti, Joanna Sadlej, and Andrzej L. Sobolewski. "Tailoring the Schiff base photoswitching – a non-adiabatic molecular dynamics study of substituent effect on excited state proton transfer." Physical Chemistry Chemical Physics 19, no. 7 (2017): 5318–25. http://dx.doi.org/10.1039/c6cp08545h.
14
Wang, Yue, Ting Wang, and Xing-Yu Zhu. "Virtual Photon-Mediated Quantum State Transfer and Remote Entanglement between Spin Qubits in Quantum Dots Using Superadiabatic Pulses." Entropy 26, no. 5 (April 29, 2024): 379. http://dx.doi.org/10.3390/e26050379.
Анотація:
Spin qubits in semiconductor quantum dots are an attractive candidate for scalable quantum information processing. Reliable quantum state transfer and entanglement between spatially separated spin qubits is a highly desirable but challenging goal. Here, we propose a fast and high-fidelity quantum state transfer scheme for two spin qubits mediated by virtual microwave photons. Our general strategy involves using a superadiabatic pulse to eliminate non-adiabatic transitions, without the need for increased control complexity. We show that arbitrary quantum state transfer can be achieved with a fidelity of 95.1% within a 60 ns short time under realistic parameter conditions. We also demonstrate the robustness of this scheme to experimental imperfections and environmental noises. Furthermore, this scheme can be directly applied to the generation of a remote Bell entangled state with a fidelity as high as 97.6%. These results pave the way for fault-tolerant quantum computation on spin quantum network architecture platforms.
15
Leyva, Verónica, Inés Corral, Ferran Feixas, Annapaola Migani, Lluís Blancafort, Jesús González-Vázquez, and Leticia González. "A non-adiabatic quantum-classical dynamics study of the intramolecular excited state hydrogen transfer in ortho-nitrobenzaldehyde." Physical Chemistry Chemical Physics 13, no. 32 (2011): 14685. http://dx.doi.org/10.1039/c1cp20620f.
16
Jiang, Mei Ling, Min Wang, and Dong Chen. "The Overview of Modeling the Thermo-Mechanical Three Dimensional Friction Stir Welding Process." Advanced Materials Research 189-193 (February 2011): 2129–33. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.2129.
Анотація:
A three dimensional thermo-mechanical model for FSW is presented. It's based on the model proposed by Alma H. Oliphant et al.[1] and Jacquin, D.et al.[2]. Velocity fields and initial plunge temperature profile are introduced in the steady state calculation of the temperature field during welding. And the non-adiabatic heat transfer conditions between the tool, the work piece, and the backing plate are also applied to the model. So a more accurate temperature will be got. It is anticipated that the model can be extended to optimize the FSW process parameters.
17
Tang, Hui, GeonHwan Cho, Mario Patinios, James A. Scobie, Carl M. Sangan, J. Michael Owen, and Gary D. Lock. "Effect of Ingress on Flow and Heat Transfer Upstream and Downstream of a Rotating Turbine Disc." Aerospace 6, no. 5 (April 26, 2019): 49. http://dx.doi.org/10.3390/aerospace6050049.
Анотація:
Ingress is the penetration of a hot mainstream gas in a turbine annulus through the rim seal into the wheel-space between the rotating turbine disc (the rotor) and the adjacent stationary casing (the stator). Purge flow is used to prevent or reduce ingress, and the sealing effectiveness relates the flow rates of the purge and ingress. In this paper, an adiabatic effectiveness is used to relate the temperatures of a thermally-insulated rotor, the purge flow and the ingress. A non-dimensional buffer parameter, Ψ, is used to relate the sealing effectiveness on the stator and the adiabatic effectiveness on the rotor, respectively. This paper reports the first experimental study of the effect of ingress and purge flow on the adiabatic temperatures of both upstream and downstream surfaces of the rotor. Measurements of concentration and swirl over a range of purge have been obtained in wheel-spaces upstream and downstream of the rotor in a turbine rig. In transient heating tests, fast-response thermocouples were used to measure the temperature of the air in the wheel-space core; simultaneously, the temperatures of the upstream and downstream rotor surfaces were determined from infra-red sensors. The extrapolated steady-state temperatures (obtained using a maximum-likelihood estimation analysis) were used to determine the adiabatic effectiveness as a function of purge flow rate. The buffer effect of the purge flow for both wheel-spaces was quantified via comparisons between the variation of Ψ with purge flow rate. It was shown that the sealing effectiveness for the downstream wheel-space was larger than for the upstream. Consequently, and consistent with the theoretical model, the buffering effect of the purge flow was shown to be smaller downstream.
18
Sara Bensilakhal, Redha Rebhi, Noureddine Hadidi, Giulio Lorenzini, Yacine Kerchiche, Younes Menni, Houari Ameur, and Hijaz Ahmad. "Bi-stability Bifurcation in Convection Double Diffusion Through a Shallow Horizontal Layer Saturated with a Complex Fluid." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 101, no. 1 (January 18, 2023): 137–59. http://dx.doi.org/10.37934/arfmts.101.1.137159.
Анотація:
The onset of non-linear convection in a porous layer saturated by a shear-thinning liquid is studied. The Carreau-Yasuda model is utilized for modeling the behavior of the working medium. Constant fluxes of heat and mass are defined on the horizontal surfaces of the cavity, while the vertical sides are assumed adiabatic. The parallel flow approximation and the finite difference approach are used to conduct the investigation analytically and numerically, respectively. The linear stability inspection of the convective and diffusive circumstances is carried out by taking into account an infinitesimal perturbation. The theory of linear stability is employed to determine the critical Rayleigh number for the motion from the rest state, Hopf bifurcation, and the transition from the stationary to oscillatory convection. Overall, the Carreau-Yasuda rheological parameters have a significant impact on the thresholds of convection. The most interesting findings of this study is highlighting the existence of a bi-stability phenomenon, i.e., the existence of two steady-state solutions, which was not observed before in non-Newtonian fluids convection.
19
Alsabery, Ammar I., Ishak Hashim, Ali J. Chamkha, Habibis Saleh, and Bilal Chanane. "Effect of spatial side-wall temperature variation on transient natural convection of a nanofluid in a trapezoidal cavity." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 6 (June 5, 2017): 1365–84. http://dx.doi.org/10.1108/hff-11-2015-0488.
Анотація:
Purpose This paper aims to study analytically and numerically the problem of transient natural convection heat transfer in a trapezoidal cavity with spatial side-wall temperature variation. Design/methodology/approach The governing equations subject to the initial and boundary conditions are solved numerically by the finite difference scheme consisting of the alternating direction implicit method and the tri-diagonal matrix algorithm. The left sloping wall of the cavity is heated to non-uniform temperature, and the right sloping wall is maintained at a constant cold temperature, while the horizontal walls are kept adiabatic. Findings It is shown that the heat transfer rate increases in non-uniform heating increments, whereby low wave number values are more affected by the convection. The best heat transfer enhancement results from larger side wall inclination angle; however, trapezoidal cavities require longer time compared to that of square to reach steady state. Originality/value The study of natural convection heat transfer in a trapezoidal cavity filled with nanofluid and heated by spatial side-wall temperature has not yet been undertaken. Thus, the authors of the present study believe that this work is valuable.
20
Spencer, Jacob, Laura Scalfi, Antoine Carof, and Jochen Blumberger. "Confronting surface hopping molecular dynamics with Marcus theory for a molecular donor–acceptor system." Faraday Discussions 195 (2016): 215–36. http://dx.doi.org/10.1039/c6fd00107f.
Анотація:
We investigate the performance of fewest switches surface hopping (SH) in describing electron transfer (ET) for a molecular donor–acceptor system. Computer simulations are carried out for a wide range of reorganisation energy (λ), electronic coupling strength (Hab) and driving force using our recently developed fragment orbital-based SH approach augmented with a simple decoherence correction. This methodology allows us to compute SH ET rates over more than four orders of magnitude, from the sub-picosecond to the nanosecond time regime. We find good agreement with semi-classical ET theory in the non-adiabatic ET regime. The correct scaling of the SH ET rate with electronic coupling strength is obtained and the Marcus inverted regime is reproduced, in line with previously reported results for a spin-boson model. Yet, we find that the SH ET rate falls below the semi-classical ET rate in the adiabatic regime, where the free energy barrier is in the order of kBT in our simulations. We explain this by first signatures of non-exponential population decay of the initial charge state. For even larger electronic couplings (Hab = λ/2), the free energy barrier vanishes and ET rates are no longer defined. At this point we observe a crossover from ET on the vibronic time scale to charge relaxation on the femtosecond time scale that is well described by thermally averaged Rabi oscillations. The extension of the analysis from the non-adiabatic limit to large electronic couplings and small or even vanishing activation barriers is relevant for our understanding of charge transport in organic semiconductors.
21
Hänni, Dominic, Rainer Schädler, Reza Abhari, Anestis Kalfas, Gregor Schmid, Ewald Lutum, and Nicolas Lecoq. "Purge flow effects on rotor hub endwall heat transfer with extended endwall contouring into the disk cavity." Journal of the Global Power and Propulsion Society 3 (May 13, 2019): 555–68. http://dx.doi.org/10.33737/jgpps/109838.
Анотація:
Efficiency improvements for gas turbines are strongly coupled with increasing turbine inlet temperatures. This imposes new challenges for designers for efficient and adequate cooling of turbine components. Modern gas turbines inject bleed air from the compressor into the stator/rotor rim seal cavity to prevent hot gas ingestion from the main flow, while cooling the rotor disk. The purge flow interacts with the main flow field and static pressure field imposed by the turbine blades. This complex interaction causes non-uniform and jet-like penetration of the purge flow into the main flow field, hence affecting the endwall heat transfer on the rotor. To improve the understanding of purge flow effects on rotor hub endwall heat transfer, an unshrouded, high-pressure representative turbine design with 3D blading and extended endwall contouring of the rotor into the cavity seal was tested. The measurements were conducted in the 1.5-stage axial turbine facility LISA at ETH Zurich, where a state-of-the-art measurement setup with a high-speed infrared camera and thermally managed rotor insert was used to perform high-resolution heat transfer measurements on the rotor. Three different purge flow rates were investigated with regard to hub endwall heat transfer. Additionally, steady-state computational fluid dynamics simulations were performed to complement the experiments. It was found that the local heat transfer rate changes up to ±20% depending on the purge flow rate. The main part of the purged air is ejected at the endwall trough location and swept towards the rotor suction side, which is caused by the interaction of main flow and the cavity extended endwall design. The presence of low momentum purge flow locally reduces the heat transfer rate. Changes in adiabatic wall temperature and heat transfer (depending on purge rate) are observed from the platform start up to the cross passage migration of the secondary flow structures.
22
Basilevsky, M. V., M. V. Vener, G. V. Davidovich, and A. V. Soudackov. "Dynamics of proton transfer reactions in polar solvent in the non-adiabatic two-state approximation: test calculations for carbon-carbon reaction centre." Chemical Physics 208, no. 2 (August 1996): 267–82. http://dx.doi.org/10.1016/0301-0104(96)00058-4.
23
Fatima, Jon Vogel, Talgat Inerbaev, Nuri Oncel, and Dmitri Kilin. "First-Principles Study of Charge Carrier Dynamics with Explicit Treatment of Momentum Dispersion on Si Nanowires along <211> crystallographic Directions." MRS Advances 3, no. 59 (2018): 3477–82. http://dx.doi.org/10.1557/adv.2018.560.
Анотація:
ABSTRACTThe ground state structure, optical properties and charge carrier dynamics of silicon nanowire (SiNW) grown in <211> crystallographic direction is studied as a function of wavevector using density functional theory. This nanowire can be used as fundamental unit of nanoelectronic devices. The optical properties are computed under assumption of momentum conservation$\Delta \vec{k} = 0$. The on-the-fly non-adiabatic couplings for electronic degrees of freedom are obtained along the ab initio molecular dynamics nuclear trajectories, which are used as parameters for Redfield density matrix equation of motion. By investigating the photo-induced process on this nanowire, it is shown that high-energy photoexcitation relaxes to the band gap edge within 75 ps. The results of these calculations help to understand the mechanism of electron transfer process on the Si nanowire.
24
Wolfrum, J. "Laser Stimulation and Observation of Simple Gas Phase Radical Reactions." Laser Chemistry 9, no. 1-3 (January 1, 1988): 171–93. http://dx.doi.org/10.1155/lc.9.171.
Анотація:
Experiments on the effect of Selective vibrational, translational and orientations excitation of reactants in bimolecular reactions can give important insights into the microscopic dynamics of elementary chemical reactions. The information obtained in such experiments can be compared with the results of theoretical calculations of the reaction dynamics based on ab initio potential energy surfaces and is also of basic interest to improve the kinetic data used in detailed chemical kinetic modelling.Rotational and vibrational energy transfer between H2 and H0 has been studied directly using Raman excitation combined with time resolved CARS spectroscopy. The competition between reactive and inelastic channels was investigated for reactions of atoms with vibrationally excited H2 and HCl molecules. Selective vibrational excitation was achieved by using infrared laser or Raman-pumping. The reaction products were detected by time resolved atomic line resonance absorption mass-spectrometry and CARS-spectroscopy. In some cases information on the contributions of adiabatic and non-adiabatic reactive pathways could be obtained. The reaction H + O2→ OH + O has been studied using translationally hot H atoms at various energies. Absolute total reactive cross-sections, nascent rotational state distributions and information on the distribution of orientations of the OH angular momentum vector using polarized dissociation and analysis laser sources have been obtained.
25
Boccelli, Stefano, and James G. McDonald. "Realizability conditions for relativistic gases with a non-zero heat flux." Physics of Fluids 34, no. 9 (September 2022): 097115. http://dx.doi.org/10.1063/5.0106214.
Анотація:
This work introduces a limitation on the minimum value that can be assumed by the energy of a relativistic gas in the presence of a non-zero heat flux. Such a limitation arises from the non-negativity of the particle distribution function and is found by solving the Hamburger moment problem. The resulting limitation is seen to recover the Taub inequality in the case of a zero heat flux but is more strict if a non-zero heat flux is considered. These results imply that, in order for the distribution function to be non-negative, (i) the energy of a gas must be larger than a minimum threshold; (ii) the heat flux, on the other hand, has a maximum value determined by the energy and the pressure tensor; and (iii) there exists an upper limit for the adiabatic index Γ of the relativistic equation of state and that limit decreases in the presence of a heat flux and pressure anisotropy, asymptoting to a value Γ = 1. The latter point implies that the Synge equation of state is formally incompatible with a relativistic gas showing a heat flux, except in certain gas states.
26
Knuth, Shelley L., and John J. Cassano. "Estimating Sensible and Latent Heat Fluxes Using the Integral Method from in situ Aircraft Measurements." Journal of Atmospheric and Oceanic Technology 31, no. 9 (September 1, 2014): 1964–81. http://dx.doi.org/10.1175/jtech-d-14-00008.1.
Анотація:
Abstract In September 2009, several Aerosonde unmanned aerial vehicles (UAVs) were flown from McMurdo Station to Terra Nova Bay, Antarctica, with the purpose of collecting three-dimensional measurements of the atmospheric boundary layer (ABL) overlying a polynya. Temperature, pressure, wind speed, and relative humidity measurements collected by the UAVs were used to calculate sensible and latent heat fluxes (SHF and LHF, respectively) during three flights. Fluxes were calculated over the depth of the ABL using the integral method, in which only measurements of the mean atmospheric state (no transfer coefficients) were used. The initial flux estimates assumed that the observations were Lagrangian. Subsequent fluxes were estimated using a robust and innovative methodology that included modifications to incorporate adiabatic and non-Lagrangian processes as well as the heat content below flight level. The SHF ranged from 12 to 485 W m−2, while the LHF ranged from 56 to 152 W m−2. The importance of properly measuring the variables used to calculate the adiabatic and non-Lagrangian processes is discussed. Uncertainty in the flux estimates is assessed both by varying the calculation methodology and by accounting for observational errors. The SHF proved to be most sensitive to the temperature measurements, while the LHF was most sensitive to relative humidity. All of the flux estimates are sensitive to the depth of the boundary layer over which the values are calculated. This manuscript highlights these sensitivities for future field campaigns to demonstrate the measurements most important for accurate flux estimates.
27
Richings, Gareth W., and Scott Habershon. "Analyzing Grid-Based Direct Quantum Molecular Dynamics Using Non-Linear Dimensionality Reduction." Molecules 26, no. 24 (December 7, 2021): 7418. http://dx.doi.org/10.3390/molecules26247418.
Анотація:
Grid-based schemes for simulating quantum dynamics, such as the multi-configuration time-dependent Hartree (MCTDH) method, provide highly accurate predictions of the coupled nuclear and electronic dynamics in molecular systems. Such approaches provide a multi-dimensional, time-dependent view of the system wavefunction represented on a coordinate grid; in the case of non-adiabatic simulations, additional information about the state populations adds a further layer of complexity. As such, wavepacket motion on potential energy surfaces which couple many nuclear and electronic degrees-of-freedom can be extremely challenging to analyse in order to extract physical insight beyond the usual expectation-value picture. Here, we show that non-linear dimensionality reduction (NLDR) methods, notably diffusion maps, can be adapted to extract information from grid-based wavefunction dynamics simulations, providing insight into key nuclear motions which explain the observed dynamics. This approach is demonstrated for 2-D and 9-D models of proton transfer in salicylaldimine, as well as 8-D and full 12-D simulations of cis-trans isomerization in ethene; these simulations demonstrate how NLDR can provide alternative views of wavefunction dynamics, and also highlight future developments.
28
Freibert, Antonia, David Mendive-Tapia, Nils Huse, and Oriol Vendrell. "Femtosecond x-ray absorption spectroscopy of pyrazine at the nitrogen K-edge: on the validity of the Lorentzian limit." Journal of Physics B: Atomic, Molecular and Optical Physics 54, no. 24 (December 22, 2021): 244003. http://dx.doi.org/10.1088/1361-6455/ac3846.
Анотація:
Abstract We calculate the femtosecond x-ray absorption spectrum of pyrazine at the nitrogen K-edge including the wavepacket dynamics in both the valence and core-excited state manifolds. We do not invoke the widely used short-time (or Lorentzian) approximation which neglects the nuclear dynamics after the x-ray probe excitation. Instead, we calculate the x-ray-induced polarization in the time-domain where the optical pump as well as x-ray probe pulses are explicitly described. While the non-adiabatic population transfer following the optical excitation is well reproduced in the Lorentzian limit the transient x-ray absorption spectra obtained under this approximation lack some vibronic features, even when considering the short core-hole lifetime of nitrogen. We further demonstrate the effect of an increasingly longer pulse on the observed photo-triggered wavepacket dynamics which are blurred to the point that the x-ray probe response becomes effectively time-independent.
29
de la Lande, Aurélien, Aurelio Alvarez-Ibarra, Karim Hasnaoui, Fabien Cailliez, Xiaojing Wu, Tzonka Mineva, Jérôme Cuny, et al. "Molecular Simulations with in-deMon2k QM/MM, a Tutorial-Review." Molecules 24, no. 9 (April 26, 2019): 1653. http://dx.doi.org/10.3390/molecules24091653.
Анотація:
deMon2k is a readily available program specialized in Density Functional Theory (DFT) simulations within the framework of Auxiliary DFT. This article is intended as a tutorial-review of the capabilities of the program for molecular simulations involving ground and excited electronic states. The program implements an additive QM/MM (quantum mechanics/molecular mechanics) module relying either on non-polarizable or polarizable force fields. QM/MM methodologies available in deMon2k include ground-state geometry optimizations, ground-state Born–Oppenheimer molecular dynamics simulations, Ehrenfest non-adiabatic molecular dynamics simulations, and attosecond electron dynamics. In addition several electric and magnetic properties can be computed with QM/MM. We review the framework implemented in the program, including the most recently implemented options (link atoms, implicit continuum for remote environments, metadynamics, etc.), together with six applicative examples. The applications involve (i) a reactivity study of a cyclic organic molecule in water; (ii) the establishment of free-energy profiles for nucleophilic-substitution reactions by the umbrella sampling method; (iii) the construction of two-dimensional free energy maps by metadynamics simulations; (iv) the simulation of UV-visible absorption spectra of a solvated chromophore molecule; (v) the simulation of a free energy profile for an electron transfer reaction within Marcus theory; and (vi) the simulation of fragmentation of a peptide after collision with a high-energy proton.
30
Alsharari, Fahad, and Mohamed M. Mousa. "New application of MOL-PACT for simulating buoyancy convection of a copper-water nanofluid in a square enclosure containing an insulated obstacle." AIMS Mathematics 7, no. 11 (2022): 20292–312. http://dx.doi.org/10.3934/math.20221111.
Анотація:
<abstract> <p>In this study, we have simulated transient and steady state free convection flow and heat transfer inside a square enclosure filled with a copper-water nanofluid of spherical shape nanoparticles following Tiwari-Das model. The cavity containing an insulated rectangular obstacle of height ranging from 0% to 50% of the cavity side-length. The vertical sides of the enclosure are kept at different temperatures, while the flat sides are assumed to be adiabatic as the obstacle. The combined method of lines/penalty-artificial compressibility technique (MOL-PACT) has been applied to solve the dimensional time dependent mathematical model after converting it into a non-dimensional structure. The combined method of lines/penalty-artificial compressibility technique is recently successfully applied to simulate free convection of MHD fluid in square enclosure with a localized heating. The extension of this promising technique for studying heat transfer of nanofluids is one of the objectives of this paper. Another objective of the study is to inspect the impact of several model parameters such as, the obstacle height, nanoparticles volume-fraction, nanoparticles radius and Rayleigh number on streamlines, temperature distribution and Nusselt number as an expression of heat transfer inside the enclosure. The results have been discussed and shown graphically. Comparisons with former results for related cases in the literature are made and reasonably good agreements are observed.</p> </abstract>
31
Diao, Li, та Peter Wan. "Chemistry of photogenerated α-phenyl-substituted o-, m-, and p-quinone methides from phenol derivatives in aqueous solution". Canadian Journal of Chemistry 86, № 2 (1 лютого 2008): 105–18. http://dx.doi.org/10.1139/v07-125.
Анотація:
The enhanced photochemical reactivity of o-substituted phenols in its propensity to give o-quinone methide (o-QM) intermediates via excited state intramolecular proton transfer (ESIPT) was uncovered by Keith Yates as part of his now classic studies of photohydration of aromatic alkenes, alkynes, and related compounds. Photogeneration of QMs and the study of their chemistry along with potential biological applications are the focus of many groups. In this work, photochemical precursors to o-, m-, and p-QMs based on substituted phenols (hydroxybenzyl alcohols) and related compounds have been studied in aqueous solution as a function of pH and water content. The focus will be on QMs that are stabilized by an α-phenyl substituent, which enhances quantum yields for their formation, with the resulting QMs having longer lifetimes and easier to detect. Noteworthy is that all QM isomers can be photogenerated with the o and m isomers being the most efficient, consistent with the Zimmerman “ortho-meta” effect. m-QMs have formal non-Kekulé structures, and although they can be routinely photogenerated, are found to be most reactive. One m-QM was found to undergo a photocondensation reaction at high pH giving rise to m-substituted oligomers. The mechanism of QM formation in aqueous solution is believed to involve singlet excited phenols that undergo adiabatic deprotonation to give the corresponding photoexcited phenolate ion, which subsequently expels the hydroxide ion (photodehydroxylation). A pathway involving direct loss of water for the o-isomers is also possible in organic solvents.Key words: quinone methides, phenols, excited state acidity, solvolysis, carbocations, meta effect, photopolymerization, non-Kekulé intermediates.
32
Karwowski, Boleslaw. "How Clustered DNA Damage Can Change the Electronic Properties of ds-DNA—Differences between GAG, GAOXOG, and OXOGAOXOG." Biomolecules 13, no. 3 (March 11, 2023): 517. http://dx.doi.org/10.3390/biom13030517.
Анотація:
Every 24 h, roughly 3 × 1017 incidences of DNA damage are generated in the human body as a result of intra- or extra-cellular factors. The structure of the formed lesions is identical to that formed during radio- or chemotherapy. Increases in the clustered DNA damage (CDL) level during anticancer treatment have been observed compared to those found in untreated normal tissues. 7,8-dihydro-8-oxo-2′-deoxyguanosine (OXOG) has been recognized as the most common lesion. In these studies, the influence of OXOG, as an isolated (oligo-OG) or clustered DNA lesion (oligo-OGOG), on charge transfer has been analyzed in comparison to native oligo-G. DNA lesion repair depends on the damage recognition step, probably via charge transfer. Here the electronic properties of short ds-oligonucleotides were calculated and analyzed at the M062x/6-31++G** level of theory in a non-equilibrated and equilibrated solvent state. The rate constant of hole and electron transfer according to Marcus’ theory was also discussed. These studies elucidated that OXOG constitutes the sink for migrated radical cations. However, in the case of oligo-OGOG containing a 5′-OXOGAXOXG-3′ sequence, the 3′-End OXOG becomes predisposed to electron-hole accumulation contrary to the undamaged GAG fragment. Moreover, it was found that the 5′-End OXOG present in an OXOGAOXOG fragment adopts a higher adiabatic ionization potential than the 2′-deoxyguanosine of an undamaged analog if both ds-oligos are present in a cationic form. Because increases in CDL formation have been observed during radio- or chemotherapy, understanding their role in the above processes can be crucial for the efficiency and safety of medical cancer treatment.
33
Pagliarini, L., F. Clemens, F. Bozzoli, L. Cattani, N. Miche, M. Bernagozzi, M. Marengo, A. A. Alqahtani, and V. Bertola. "Infrared measurements of fluid temperature in a polymeric Pulsating Heat Pipe." Journal of Physics: Conference Series 2685, no. 1 (January 1, 2024): 012050. http://dx.doi.org/10.1088/1742-6596/2685/1/012050.
Анотація:
Abstract Pulsating heat pipes are two-phase passive heat transfer devices partially filled with a working fluid in saturation conditions. During operation, supplying heat to one end of the system (named evaporator) results in a local increase in temperature and pressure, which drives the fluid through a transport section (named adiabatic section) towards the cooled, opposite end (named condenser) for effective heat dissipation. The local thermo-fluid dynamic state of the working fluid is sometimes assessed by means of non-intrusive techniques, such as infrared thermography. In this case, the radiative properties of the systems in the infrared spectrum must be known a priori. Nevertheless, since pulsating heat pipes may be manufactured with different materials, wall thicknesses and channel geometries, the radiative properties of the walls and the confined flow are not always known or assessable by means of the available literature. Hence, the work proposes to design a straightforward calibration procedure for quantitative infrared fluid temperature measurements in a polymeric pulsating heat pipe charged with FC-72 and having unknown radiative properties. The emissivity and transmissivity of the walls and confined fluid are estimated with good accuracy. The results will allow repeatable and reliable fluid temperature measurements in future experimentations on the mentioned device.
34
Camci, C., and B. Glezer. "Liquid Crystal Thermography on the Fluid Solid Interface of Rotating Systems." Journal of Heat Transfer 119, no. 1 (February 1, 1997): 20–29. http://dx.doi.org/10.1115/1.2824095.
Анотація:
Liquid crystal thermography is an effective method widely employed in transient and steady-state heat transfer experiments with excellent spatial resolution and good accuracy. Most of the past studies in liquid crystal thermography deal with stationary conditions. The present investigation deals with the influence of rotation on the color response of encapsulated liquid crystals attached to a flat rotating surface. A general methodology developed for the application of thermochromic liquid crystals in rotating systems is described for the first time. The investigation is performed for a rotational speed range from 0 to 7500 rpm using two different coatings displaying red at 30° and 45°C, under stationary conditions. Local liquid crystal color on the surface of a rotating disk is correlated with local temperature as measured by a non-intrusive infrared sensor at various rotational speeds. An immediate observation from the present study is that the color response (hue) of encapsulated liquid crystals is not altered by either the centrifugal acceleration of the rotating environment or the aerodynamic friction force at the rotating disk-air interface. Present investigation also shows that when a stroboscope light is introduced, the color response is not significantly altered due to additional periodic illumination. A complete and general experimental methodology including rotating surfaces with non-axisymmetric temperature distribution is presented. Results from the current liquid crystal technique agree well with the theoretical adiabatic temperature rise of a free rotating disk as predicted by an analytical method.
35
Farjallah, Mohamed, Dibyendu Sardar, Bimalendu Deb, and Hamid Berriche. "Electronic Structure, Spectroscopy, Cold Ion–Atom Elastic Collision Properties, and Photoassociation Formation Prediction of the (MgCs)+ Molecular Ion." Atoms 11, no. 9 (September 15, 2023): 121. http://dx.doi.org/10.3390/atoms11090121.
Анотація:
In this paper, we extensively study the electronic structure, interactions, and dynamics of the (MgCs)+ molecular ion. The exchanges between the alkaline atom and the low-energy cationic alkaline earths, which are important in the field of cold and ultracold quantum chemistry, are studied. We use an ab initio approach based on the formalism of non-empirical pseudo-potential for Mg2+ and Cs+ cores, large Gaussian basis sets, and full-valence configuration interaction. In this context, the (MgCs)+ cation is treated as an effective two-electron system. Adiabatic potential energy curves and their spectroscopic constants for the ground and the first 20 excited states of 1,3Σ+ symmetries are determined. Furthermore, we identify the avoided crossings between the electronic states of 1,3Σ+ symmetries. These crossings are related to the charge transfer process between the two ionic limits, Mg/Cs+ and Mg+/Cs. Therefore, vibrational-level spacings and the transition and permanent dipole moments are presented and analyzed. Using the produced potential energy data, the ground-state scattering wave functions and elastic cross-sections are calculated for a wide range of energies. In addition, we predict the formation of a translationally and rotationally cold molecular ion (MgCs)+ in the ground-state electronic potential energy through a stimulated Raman-type process aided by ion–atom cold collision. In the low-energy limit (<1 mK), elastic scattering cross-sections exhibit Wigner law threshold behavior, while in the high-energy limit, the cross-sections act as a function of energy E go as E−1/3. A qualitative discussion about the possibilities of forming cold (MgCs)+ molecular ions by photoassociative spectroscopy is presented.
36
Dutta Pal, Gopa, Bipan Dutta, Tapan Ganguly, and Joydeep Chowdhury. "Role of gold nanocolloids on the photostability of 2-hydroxy-5-methyl benzaldehyde molecule and evidence of excited state intramolecular proton transfer process aided by DFT, non-adiabatic Ab Initio molecular dynamics simulations." Journal of Luminescence 188 (August 2017): 378–87. http://dx.doi.org/10.1016/j.jlumin.2017.04.038.
37
Karwowski, Boleslaw T. "The Influence of Oxidized Imino-Allantoin in the Presence of OXOG on Double Helix Charge Transfer: A Theoretical Approach." International Journal of Molecular Sciences 25, no. 11 (May 29, 2024): 5962. http://dx.doi.org/10.3390/ijms25115962.
Анотація:
The genome is continuously exposed to a variety of harmful factors that result in a significant amount of DNA damage. This article examines the influence of a multi-damage site containing oxidized imino-allantoin (OXIa) and 7,8-dihydro-8-oxo-2′-deoxyguanosine (OXOdG) on the spatial geometry, electronic properties, and ds-DNA charge transfer. The ground stage of a d[A1OXIa2A3OXOG4A5]*d[T5C4T3C2T1] structure was obtained at the M06-2X/6-D95**//M06-2X/sto-3G level of theory in the condensed phase, with the energies obtained at the M06-2X/6-31++G** level. The non-equilibrated and equilibrated solvent-solute interactions were also considered. Theoretical studies reveal that the radical cation prefers to settle on the OXOG moiety, irrespective of the presence of OXIa in a ds-oligo. The lowest vertical and adiabatic ionization potential values were found for the OXOG:::C base pair (5.94 and 5.52 [eV], respectively). Conversely, the highest vertical and adiabatic electron affinity was assigned for OXIaC as follows: 3.15 and 3.49 [eV]. The charge transfers were analyzed according to Marcus’ theory. The highest value of charge transfer rate constant for hole and excess electron migration was found for the process towards the OXOGC moiety. Surprisingly, the values obtained for the driving force and activation energy of electro-transfer towards OXIa2C4 located this process in the Marcus inverted region, which is thermodynamically unfavorable. Therefore, the presence of OXIa can slow down the recognition and removal processes of other DNA lesions. However, with regard to anticancer therapy (radio/chemo), the presence of OXIa in the structure of clustered DNA damage can result in improved cancer treatment outcomes.
38
Wang, Yifan, Sai Vudata, Paul Brooker, and James M. Fenton. "(Digital Presentation) Integration of Renewable Hydrogen Production, Compression and Storage for Mobile and Stationary Fuel Cells." ECS Meeting Abstracts MA2022-01, no. 39 (July 7, 2022): 1733. http://dx.doi.org/10.1149/ma2022-01391733mtgabs.
Анотація:
With the rapid increase in the photovoltaic (PV) installations, the intermittency and the variability of the solar energy sources will lead to the frequent and steep ramping operation of conventional fossil generation. Consequently, energy storage is required for efficient use of the renewable energy source. Hydrogen production via electrolysis can provide both short and long duration capacity as a controllable load to reduce grid fluctuations and improve the resilience of the energy system. Once the hydrogen is produced, it must be stored before it is consumed. High pressure gaseous hydrogen storage is the most popular and mature hydrogen storage technology due to the technical simplicity, reliability, energy efficiency as well as affordability [1]. Compressed hydrogen storage with a fast filling-emptying rate can be used as a hydrogen multiple-purpose station for both stationary fuel cell and fuel cell electric vehicle (FCEV) applications. Although hydrogen electrolyzers, stationary fuel cells, and FCEV refueling stations have been extensively studied, little work has been done integrating these hydrogen technologies with a utility PV field to ensure electric grid stability, maximize PV utilization and efficiently produce and consume hydrogen. A model for a complete system of hydrogen production via electrolysis and high-pressure hydrogen storage was developed. The dynamic performance of different hydrogen storage filling and emptying operations with electrolyzer, stationary fuel cell and FCEV shows the feasibility and flexibility of the integrated hydrogen system. A high-fidelity dynamic model of a Proton Exchange Membrane (PEM) electrolyzer was developed for hydrogen production from PV electricity. A parallel multi-stage hydrogen compression system with cascade tanks for filling/emptying was designed and modeled. A non-adiabatic lumped dynamic model was developed for the storage tank with heat transfer from the tank to ambient air. The Soave-Redlich-Kwong equation of state was adopted to account for the non-ideal gas response of high-pressure gaseous hydrogen [2]. The 1 MW electrolyzer under full load produces hydrogen at 200 Nm3/hr (17.7 kg/hr) and the hydrogen can be compressed up to the maximum pressure of 45 MPa suitable for heavy-duty fuel cell vehicles. The storage tanks can be filled with constant/varied hydrogen flow from the electrolyzer depending on the PV power. The compressor and heat exchanger duties as well as the storage tank pressure and temperature are monitored and controlled. The tanks can be discharged to the stationary fuel cell and/or FCEVs. The dynamic performance of integrated hydrogen system for PV smoothing (filling with varied hydrogen flow in short time-scale), peak shaving (filling and emptying with constant hydrogen flow in long time-scale) and FCEV refueling (cascade filling and emptying) will be presented. The feasibility and flexibility of integrated hydrogen production and storage system for grid operation will be shown. [1] Li, Mengxiao, Yunfeng Bai, Caizhi Zhang, Yuxi Song, Shangfeng Jiang, Didier Grouset, and Mingjun Zhang. "Review on the research of hydrogen storage system fast refueling in fuel cell vehicle." International Journal of Hydrogen Energy 44, no. 21 (2019): 10677-10693. [2] Xiao, Lei, Jianye Chen, Yimei Wu, Wei Zhang, Jianjun Ye, Shuangquan Shao, and Junlong Xie. "Effects of pressure levels in three-cascade storage system on the overall energy consumption in the hydrogen refueling station." International Journal of Hydrogen Energy 46, no. 61 (2021): 31334-31345.
39
Lazzi Gazzini, Sebastiano, Rainer Schädler, Anestis I. Kalfas, Reza S. Abhari, Sebastian Hohenstein, Gregor Schmid, and Ewald Lutum. "Effect of purge air on rotor endwall heat transfer of an axial turbine." Journal of the Global Power and Propulsion Society 1 (October 12, 2017): F29ZWY. http://dx.doi.org/10.22261/f29zwy.
Анотація:
AbstractIn order to gain in cycle efficiency, turbine inlet temperatures tend to rise, posing the challenge for designers to cool components more effectively. Purge flow injection through the rim seal is regularly used in gas turbines to limit the ingestion of hot air in the cavities and prevent overheating of the disks and shaft bearings. The interaction of the purge air with the main flow and the static pressure field of the blade rows results in a non-homogenous distribution of coolant on the passage endwall which poses questions on its effect on endwall heat transfer. A novel measurement technique based on infrared thermography has been applied in the rotating axial turbine research facility LISA of the Laboratory for Energy Conversion (LEC) of ETH Zürich. A 1.5 stage configuration with fully three-dimensional airfoils and endwall contouring is integrated in the facility. The effect of different purge air mass flow rates on the distribution of the heat transfer quantities has been observed for the rated operating condition of the turbine. Two-dimensional distributions of Nusselt number and adiabatic wall temperature show that the purge flow affects local heat loads. It does so by acting on the adiabatic wall temperature on the suction side of the passage until 30% of the axial extent of the rotor endwall. This suggests the possibility of effectively employing purge air also as rotor platform coolant in this specific region. The strengthening of the secondary flows due to purge air injection is observed, but plays a negligible role in varying local heat fluxes. For one test case, experimental data is compared to high-fidelity, unsteady Reynolds-Averaged Navier–Stokes simulations performed on a model of the full 1.5 stage configuration.
40
SHARAFUTDINOV, Ramil F., and Filyus F. Davletshin. "AN ANALYTICAL MODEL OF A NON-STATIONARY TEMPERATURE FIELD IN A RESERVOIR WITH A HYDRAULIC FRACTURING." Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy 7, no. 2 (2021): 75–94. http://dx.doi.org/10.21684/2411-7978-2021-7-2-75-94.
Анотація:
At the present stage of development of the oil and gas industry, considerable attention is paid to methods of increasing oil recovery of productive reservoirs. One of the most popular methods of intensifying oil production today is hydraulic fracturing. The efficiency and success of hydraulic fracturing largely depends on the parameters of the formed fracture; in this regard, the development of methods for evaluating the parameters of hydraulic fracturing fractures is an urgent task. Non-stationary thermometry is a promising area for monitoring the quality of hydraulic fracturing. To date, thermometry is used to localize the locations of multiple fractures in horizontal wells. In this paper, we study the application of non-stationary thermometry for estimating the parameters of a vertical hydraulic fracturing fracture. An analytical model of non-isothermal single-phase fluid filtration in a reservoir with a vertical fracture is developed. To calculate the temperature field in the formation and the fracture, the convective heat transfer equation is used, taking into account the thermodynamic effects (Joule — Thomson and adibatic), for the fracture, the heat and mass transfer between the fracture and the formation area is also taken into account. To assess the correctness of the model, the analytical solution is compared with the results of numerical modeling in the Ansys Fluent software package. The nonstationary temperature field is calculated for the constant sampling mode. It is established that at the initial moment of time after the well start-up, a negative temperature anomaly is formed due to the adiabatic effect, the value of which increases with a decrease in the fracture width. Over time, the temperature of the fluid flowing into the well increases due to the Joule — Thomson effect, and the value of the positive temperature anomaly increases as the width and permeability of the fracture decreases due to an increase in the pressure gradient in it. The developed analytical model can be used to solve inverse problems for estimating hydraulic fracturing parameters based on non-stationary temperature measurements in the wellbore of producing wells.
41
POPE, ALLEN, IAN C. WILLIS, FINNUR PÁLSSON, NEIL S. ARNOLD, W. GARETH REES, HELGI BJÖRNSSON, and LAUREN GREY. "Elevation change, mass balance, dynamics and surging of Langjökull, Iceland from 1997 to 2007." Journal of Glaciology 62, no. 233 (April 18, 2016): 497–511. http://dx.doi.org/10.1017/jog.2016.55.
Анотація:
ABSTRACTGlaciers and ice caps around the world are changing quickly, with surge-type behaviour superimposed upon climatic forcing. Here, we study Iceland's second largest ice cap, Langjökull, which has both surge- and non-surge-type outlets. By differencing elevation change with surface mass balance, we estimate the contribution of ice dynamics to elevation change. We use DEMs, in situ stake measurements, regional reanalyses and a mass-balance model to calculate the vertical ice velocity. Thus, we not only compare the geodetic, modelled and glaciological mass balances, but also map spatial variations in glacier dynamics. Maps of emergence and submergence velocity successfully highlight the 1998 surge and subsequent quiescence of one of Langjökull's outlets by visualizing both source and sink areas. In addition to observing the extent of traditional surge behaviour (i.e. mass transfer from the accumulation area to the ablation area followed by recharge of the source area), we see peripheral areas where the surge impinged upon an adjacent ridge and subsequently retreated. While mass balances are largely in good agreement, discrepancies between modelled and geodetic mass balance may be explained by inaccurate estimates of precipitation, saturated adiabatic lapse rate or degree-day factors. Nevertheless, the study was ultimately able to investigate dynamic surge behaviour in the absence of in situ measurements during the surge.
42
Cerezo, Javier, Sheng Gao, Nicola Armaroli, Francesca Ingrosso, Giacomo Prampolini, Fabrizio Santoro, Barbara Ventura, and Mariachiara Pastore. "Non-Phenomenological Description of the Time-Resolved Emission in Solution with Quantum–Classical Vibronic Approaches—Application to Coumarin C153 in Methanol." Molecules 28, no. 9 (May 5, 2023): 3910. http://dx.doi.org/10.3390/molecules28093910.
Анотація:
We report a joint experimental and theoretical work on the steady-state spectroscopy and time-resolved emission of the coumarin C153 dye in methanol. The lowest energy excited state of this molecule is characterized by an intramolecular charge transfer thus leading to remarkable shifts of the time-resolved emission spectra, dictated by the methanol reorganization dynamics. We selected this system as a prototypical test case for the first application of a novel computational protocol aimed at the prediction of transient emission spectral shapes, including both vibronic and solvent effects, without applying any phenomenological broadening. It combines a recently developed quantum–classical approach, the adiabatic molecular dynamics generalized vertical Hessian method (Ad-MD|gVH), with nonequilibrium molecular dynamics simulations. For the steady-state spectra we show that the Ad-MD|gVH approach is able to reproduce quite accurately the spectral shapes and the Stokes shift, while a ∼0.15 eV error is found on the prediction of the solvent shift going from gas phase to methanol. The spectral shape of the time-resolved emission signals is, overall, well reproduced, although the simulated spectra are slightly too broad and asymmetric at low energies with respect to experiments. As far as the spectral shift is concerned, the calculated spectra from 4 ps to 100 ps are in excellent agreement with experiments, correctly predicting the end of the solvent reorganization after about 20 ps. On the other hand, before 4 ps solvent dynamics is predicted to be too fast in the simulations and, in the sub-ps timescale, the uncertainty due to the experimental time resolution (300 fs) makes the comparison less straightforward. Finally, analysis of the reorganization of the first solvation shell surrounding the excited solute, based on atomic radial distribution functions and orientational correlations, indicates a fast solvent response (≈100 fs) characterized by the strengthening of the carbonyl–methanol hydrogen bond interactions, followed by the solvent reorientation, occurring on the ps timescale, to maximize local dipolar interactions.
43
Wu, JiaHui, Xiaohang Chen, Shu-Hua Xia, Ganglong Cui, and Yan Zhang. "Excited-state Photochemistry Dynamics of 2-(1-naphthyl) phenol: Electronic Structure Calculations and Non-adiabatic Dynamics Simulations." Physical Chemistry Chemical Physics, 2022. http://dx.doi.org/10.1039/d2cp03283j.
Анотація:
Excited-state proton transfer processes and the formation mechanisms of quinone methides were investigated of (1-naphthyl)phenol by combining static electronic structures calculations and non-adiabatic dynamics simulations in the vacuum. The results...
44
Ferté, Anthony, Axel Houssin, Nina Albouy, Isabella C. D. Merritt, and Morgane Vacher. "ESIPT in the Pyrrol Pyridine molecule: Mechanism, timescale and yield revealed using dynamics simulations." Physical Chemistry Chemical Physics, 2023. http://dx.doi.org/10.1039/d3cp00026e.
Анотація:
Excited State Intramolecular Proton Transfer in Pyrrol Pyridine is theoretically investigated using non-adiabatic dynamics simulations. The photochemical process is completely characterised: the reaction time, the total yield and the accessibility...
45
Bennett, Olivia, Antonia Freibert, K. Eryn Spinlove, and Graham A. Worth. "Prediction through quantum dynamics simulations: Photo-excited cyclobutanone." Journal of Chemical Physics 160, no. 17 (May 1, 2024). http://dx.doi.org/10.1063/5.0203654.
Анотація:
Quantum dynamics simulations are becoming a standard tool for simulating photo-excited molecular systems involving a manifold of coupled states, known as non-adiabatic dynamics. While these simulations have had many successes in explaining experiments and giving details of non-adiabatic transitions, the question remains as to their predictive power. In this work, we present a set of quantum dynamics simulations on cyclobutanone using both grid-based multi-configuration time-dependent Hartree and direct dynamics variational multi-configuration Gaussian methods. The former used a parameterized vibronic coupling model Hamiltonian, and the latter generated the potential energy surfaces on the fly. The results give a picture of the non-adiabatic behavior of this molecule and were used to calculate the signal from a gas-phase ultrafast electron diffraction (GUED) experiment. Corresponding experimental results will be obtained and presented at a later stage for comparison to test the predictive power of the methods. The results show that over the first 500 fs after photo-excitation to the S2 state, cyclobutanone relaxes quickly to the S1 state, but only a small population relaxes further to the S0 state. No significant transfer of population to the triplet manifold is found. It is predicted that the GUED experiments over this time scale will see signals related mostly to the C–O stretch motion and elongation of the molecular ring along the C–C–O axis.
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Fay, Thomas P. "Extending non-adiabatic rate theory to strong electronic couplings in the Marcus inverted regime." Journal of Chemical Physics 161, no. 1 (July 1, 2024). http://dx.doi.org/10.1063/5.0218653.
Анотація:
Electron transfer reactions play an essential role in many chemical and biological processes. Fermi’s golden rule (GR), which assumes that the coupling between electronic states is small, has formed the foundation of electron transfer rate theory; however, in short range electron/energy transfer reactions, this coupling can become very large, and, therefore, Fermi’s GR fails to make even qualitatively accurate rate predictions. In this paper, I present a simple modified GR theory to describe electron transfer in the Marcus inverted regime at arbitrarily large electronic coupling strengths. This theory is based on an optimal global rotation of the diabatic states, which makes it compatible with existing methods for calculating GR rates that can account for nuclear quantum effects with anharmonic potentials. Furthermore, the optimal GR (OGR) theory can also be combined with analytic theories for non-adiabatic rates, such as Marcus theory and Marcus–Levich–Jortner theory, offering clear physical insights into strong electronic coupling effects in non-adiabatic processes. OGR theory is also tested on a large set of spin-boson models and an anharmonic model against exact quantum dynamics calculations, where it performs well, correctly predicting rate turnover at large coupling strengths. Finally, an example application to a boron-dipyrromethane–anthracene photosensitizer reveals that strong coupling effects inhibit excited state charge recombination in this system, reducing the rate of this process by a factor of 4. Overall, OGR theory offers a new approach to calculating electron transfer rates at strong couplings, offering new physical insights into a range of non-adiabatic processes.
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Shen, Yuan, Giampiero Marchegiani, Gianluigi Catelani, Luigi Amico, Ai Qun Liu, Weijun Fan, and Leong Chuan Kwek. "GHZ-like states in the Qubit-Qudit Rabi model." SciPost Physics 11, no. 6 (December 1, 2021). http://dx.doi.org/10.21468/scipostphys.11.6.099.
Анотація:
We study a Rabi type Hamiltonian system in which a qubit and a dd-level quantum system (qudit) are coupled through a common resonator. In the weak and strong coupling limits the spectrum is analysed through suitable perturbative schemes. The analysis show that the presence of the multilevels of the qudit effectively enhance the qubit-qudit interaction. The ground state of the strongly coupled system is found to be of Greenberger-Horne-Zeilinger (GHZ) type. Therefore, despite the qubit-qudit strong coupling, the nature of the specific tripartite entanglement of the GHZ state suppresses the bipartite entanglement. We analyze the system dynamics under quenching and adiabatic switching of the qubit-resonator and qudit-resonator couplings. In the quench case, we found that the non-adiabatic generation of photons in the resonator is enhanced by the number of levels in the qudit. The adiabatic control represents a possible route for preparation of GHZ states. Our analysis provides relevant information for future studies on coherent state transfer in qubit-qudit systems.
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Lognon, Elise, Alain Burger, Elise Dumont, and Antonio Monari. "Effect of Microhydration in Tuning the Photophysical Behavior of a Luminescent DNA Probe Revealed by Non‐Adiabatic Dynamics." ChemPhotoChem, April 17, 2024. http://dx.doi.org/10.1002/cptc.202400078.
Анотація:
We report the non‐adiabatic dynamics, performed in the surface hopping formalism, of an environment‐dependent luminescent organic DNA probe. In particular we have shown that the first shell solvent water molecules undergo a rather complex reorganization upon light excitation. This involves also the triggering of a water‐mediated proton transfer process which leads to the formation of the tautomeric structure. The presence of this solvent‐mediated transfer mechanism globally diminishes the intersystem crossing efficiency, and hence the population of the triplet state manifold, as compared to the non‐solvated systems. Our results also point out the non‐innocent role of solvent networks in tuning complex photophysical processes, while opening competitive relaxation channels.
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Chen, Zhao-Xian, Yu-Gui Peng, Ze-Guo Chen, Yuan Liu, Peng Chen, Xue-Feng Zhu, and Yan-Qing Lu. "Robust temporal adiabatic passage with perfect frequency conversion between detuned acoustic cavities." Nature Communications 15, no. 1 (February 17, 2024). http://dx.doi.org/10.1038/s41467-024-45932-6.
Анотація:
AbstractFor classical waves, phase matching is vital for enabling efficient energy transfer in many scenarios, such as waveguide coupling and nonlinear optical frequency conversion. Here, we propose a temporal quasi-phase matching method and realize robust and complete acoustical energy transfer between arbitrarily detuned cavities. In a set of three cavities, A, B, and C, the time-varying coupling is established between adjacent elements. Analogy to the concept of stimulated Raman adiabatic passage, amplitudes of the two couplings are modulated as time-delayed Gaussian functions, and the couplings’ signs are periodically flipped to eliminate temporal phase mismatching. As a result, robust and complete acoustic energy transfer from A to C is achieved. The non-reciprocal frequency conversion properties of our design are demonstrated. Our research takes a pivotal step towards expanding wave steering through time-dependent modulations and is promising to extend the frequency conversion based on state evolution in various linear Hermitian systems to nonlinear and non-Hermitian regimes.
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Quashie, Edwin E., Xavier Andrade, and Alfredo A. Correa. "Directional dependency of electronic stopping in nickel, projectile’s excited charge state and momentum transfer." European Physical Journal D 75, no. 11 (October 29, 2021). http://dx.doi.org/10.1140/epjd/s10053-021-00266-6.
Анотація:
AbstractWe studied the directional dependency of electronic stopping power of swift light ions in nickel using real-time time-dependent density functional theory. We report a variation of electronic stopping for moving ions as the projectile probes different electronic densities of the host material. These results show that while the predicted magnitude stays in reasonable agreement with experiment, for $$v > 2$$ v > 2 . a.u. simulating only low index crystallographic directions is not enough to sample the experimental average values. The ab initio simulations give us access to microscopic quantities, such as non-adiabatic forces, momentum transfer and transient excited state charges of the projectile and host ions, which are not available through other methods. We report these quantities for the first time.