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关键词： artificial intelligence   congestion   pulmonary blood volume   pulmonary transit time   quantitative perfusion  

摘要： Corresponding Author

关键词： Granular flow   Magnetic resonance imaging   Silo   Hopper   Velocity mapping   Solid fraction  

摘要： This work uses a recently developed MRI method to measure the solid fraction and velocity in three-dimensional (3D) hoppers quantitatively. We demonstrate that the measurements are quantitative by calculating the mass flow rate within the hopper using MRI and show good agreement with the mass flow rate measured gravimetrically. We study the velocity and solid fraction in hoppers with various angles and outlet sizes. We show that the solid fraction decreases smoothly from the bulk value above the outlet, indicating that the assumption of a "free-fall arch" used in some mass flow correlations is invalid. Furthermore, we show that the solid fraction, velocity and vertical evolution of the acceleration are all self-similar when normalised by the value at the centre of the outlet in a 3D hopper, in agreement with recent studies of 2D hoppers. Thus, these quantitative measurements enable evaluation of phenomenological models describing the flow rate from hoppers. (C) 2021 Elsevier B.V. All rights reserved.

关键词： (p, q)-Laplacian   Constant sign and nodal solutions   Critical groups   Unique continuation   Nonlinear regularity  

摘要： We consider a parametric (p, q)-equations with sign-changing reaction and Robin boundary condition. We show that for all values of the *** than a certain value which we determine precisely, the problem has at least three nontrivial solutions all with sign information and ordered. For the particular case of (p, 2)-equations we produce a second nodal solution, for a total of four nontrivial solutions. Under symmetry conditions, we show the existence of infinitely many nodal solutions. The same results are also valid for the Dirichlet problem. (c) 2021 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： nonlinear Ginzburg-Landau equation   Fractional Laplacian   Unique solvability   Convergence   Error estimate in maximum norm  

摘要： Y In this paper, we propose a three-level linearized finite difference scheme for the high-dimensional nonlinear Ginzburg-Landau equation with fractional Laplacian. The Crank-Nicolson scheme is used for time discretization, and the fractional Laplacian is discretized by the fractional centered difference scheme. The proposed difference scheme (i.e. a linear system) can be solved efficiently by fast Fourier transform (FFT) and complex conjugate gradient method, since the coefficient matrix is a multi-level block Toeplitz matrix. Furthermore, we analyze the unique solvability and boundedness of solution of the difference scheme by the discrete energy method. It is also proved that the difference scheme is unconditionally stable and second-order accurate in time and space with respect to l(infinity)-norm. Finally, several numerical examples are provided to validate the theoretical results. (C) 2021 Elsevier B.V. All rights reserved.

关键词： quantum correlations   classical external field   entanglement sudden death and birth   static noise  

摘要： We address the time evolution of quantum correlations (QC) such as entanglement, purity, and coherence for a model of two non-interacting qubits initially prepared as a maximally entangled bipartite state. We contrast the comparative potential of the classical fields to preserve these QCs in the noisy and noiseless realms. We also disclose the characteristic dynamical behavior of the QCs of the two-qubit state under the static noise effects originating from the common and different configuration models. We show that there is a direct connection between the fluctuations allowed by an environment and the preservation of QCs. Due to the static noise dephasing effects, the QCs are suppressed, resulting in the separability of the two-qubit entangled state after a finite duration. For bipartite QCs preservation, we show that the common configuration is more resourceful than the different configuration. Furthermore, this protection of the QCs under static noise for large intervals is entirely attributable to the existence of the entanglement sudden death and birth phenomenon. Most importantly, we found the bipartite QCs less fragile than the tripartite ones in comparison under the static noise. In addition, we find the concurrence measure to show more evident revivals of entanglement in comparison.

关键词： Excited state proton transfer   Quantum dynamics   Nonadiabatic effects   Spectroscopy   Coherences  

摘要： The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone. [GRAPHICS] .

关键词： 量子力学  

ISBN: (纸本)9787312051883

摘要： 本书是作者通过研读量子信息的教材和对量子信息一线科研工作者的采访, 并结合自己两年多来对量子信息方面进行的科普工作整理而成的, 介绍了量子信息的逻辑框架并对科学原理进行了解释, 并且以问答方式阐述了现在社会上人民对量子技术的一些疑惑。

关键词： Fault diagnosis   Rolling bearing   Laplacian regularization   K-nearest neighbor graph   Graph Laplacian matrix  

摘要： How to design a reasonable classification method to identify the states is a critical step in rolling bearing fault diagnosis. Along with labeled samples, the Laplacian regularization (LapR) classification method, a graph-based semi-supervised learning algorithm, can also exploit the wealth of numerous cheap unlabeled samples to obtain acceptable performance. Based on the LapR classification method, a novel fault diagnosis method of rolling bearing is put forward. First, the vibration datasets or feature datasets are constructed into an undirected and weighted K-nearest neighbor graph, which can fully reflect the similarity between dataset elements. Then, the labels of all the dataset elements are interpreted as graph signals which are indexed by the represented graph's vertices. Finally, when the constraint given by the known dataset elements is satisfied, the labels of the unknown dataset elements can be determined by finding a graph signal with minimal total variation. Experimental results reveal that whether the vibration datasets or feature datasets are analyzed, the LapR classification method is obviously superior to the popularly known classification methods in identifying the rolling bearing states especially when there are very few known samples. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Community detection   Quasi-Laplacian centrality   Node similarity   Laplacian centrality peaks clustering  

摘要： Searching for key nodes in social networks and clustering communities are indispensable components in community detection methods. With the wide application demand of detecting community networks, more and more algorithms have been proposed. Laplacian centrality peaks clustering (LPC) is an efficient and simple algorithm which is proposed on the basis of density peaks clustering (DPC) to identify clusters without parameters and prior knowledge. Before LPC is widely applied in community detection algorithms, some shortcomings should be addressed. Firstly, LPC fails to search for key nodes in networks accurately because of the similarity calculation method. Secondly, it takes too much time for LPC to calculate the Laplacian centrality of each point. To address these issues, a community detection algorithm based on Quasi-Laplacian centrality peaks clustering (CD-QLPC) is proposed after studying the advantages of Quasi-Laplacian centrality which can replace density or Laplacian centrality to characterize the importance of nodes in networks. Quasi-Laplacian centrality is obtained by the degree of each node directly, which needs less time than Laplacian centrality. In addition, a trust-based function is utilized to obtain the similarity accurately. Moreover, a new modularity-based merging strategy is adopted to identify the optimal number of communities adaptively. Experimental results show that CD-QLPC outperforms many state-of-the-art methods on both real-world networks and synthetic networks.

关键词： Quantum asymmetry   Quantum entanglement   Quantum coherence   Magnetic dipolar interaction  

摘要： We investigate the asymmetry properties of quantum states in relation to the Hamiltonian responsible for the magnetic dipolar interaction (MDI) dynamics, and we evaluate its relationship to entanglement production. We consider some classes of pure and mixed quantum states of two qubits evolved under MDI and, using the asymmetry measure defined via the Wigner-Yanase skew information, we describe the asymmetry dependence on the Hamiltonian parameters and initial conditions of the system. In addition, we define and calculate the dynamics of the asymmetry of local states, characterizing their temporal and interaction parameters dependence. Finally, because the MDI Hamiltonian has a null eigenvalue, the group generator-based asymmetry measure does not adequately quantify the state susceptibility with respect to the action of the subspace generated by the eigenvectors associated with this eigenvalue. For this reason, we also define and study the group element-based asymmetry measure with relation to the unitary operator associated with the MDI Hamiltonian.