Abstract
Matter transport is a fundamental process in nature. Understanding and manipulating flow in a synthetic media often have rich implications for modern device design. Here we experimentally ...demonstrate directional transport of photons in a two-dimensional quantum walk, where the light propagation is highly tunable through dissipation and synthetic magnetic flux. The directional flow hereof underlies the emergence of the non-Hermitian skin effect, with its orientation continuously adjustable through the photon-loss parameters. By contrast, the synthetic magnetic flux originates from an engineered geometric phase, which, by inducing localized cyclotron orbits, suppresses the bulk flow through magnetic confinement. We further demonstrate how the directional flow and synthetic flux impact the dynamics of the Floquet topological edge modes along an engineered boundary. Our results exemplify an intriguing strategy for engineering directed light transport, highlighting the interplay of non-Hermiticity and gauge fields in synthetic systems of higher dimensions.
In this paper, we consider the numerical solution of the time‐fractional telegraph equation with a nonlocal boundary condition. A novel barycentric Lagrange interpolation collocation method is ...developed to solve this equation. Two difficulties have been sorted: the singularity of the integration and the higher accuracy. At the same, we put forward a steady barycentric Lagrange interpolation technique to overcome the new “Runge” phenomenon in computation. Error estimates of the barycentric Lagrange interpolation and the time‐fractional telegraph system for the present method are presented in Sobolev spaces. High convergence rates of the proposed method are obtained and are consisted with the numerical values. Especially in the time dimension, we get the error bound, Ohnt−2 for h‐refinement and Oeht/2nt−2nt−2 for nt‐density in the L2 norms. The numerical results obtained show that the proposed numerical algorithm is accurate and computationally efficient for solving time‐fractional telegraph equation. Experiments demonstrate the high convergence rates of the proposed method are consisted with the theoretical values.
In this paper, a class of generalized shift-splitting preconditioners with two shift parameters are implemented for nonsymmetric saddle point problems with nonsymmetric positive definite (1, 1) ...block. The generalized shift-splitting (GSS) preconditioner is induced by a generalized shift-splitting of the nonsymmetric saddle point matrix, resulting in an unconditional convergent fixed-point iteration. By removing the shift parameter in the (1, 1) block of the GSS preconditioner, a deteriorated shift-splitting (DSS) preconditioner is presented. Some useful properties of the DSS preconditioned saddle point matrix are studied. Finally, numerical experiments of a model Navier–Stokes problem are presented to show the effectiveness of the proposed preconditioners.
Endoscopic resection has been successfully used for the removal of digestive submucosal tumors (SMTs). However, the cardia has been considered a challenging location for endoscopic resection due to ...its narrow lumen and sharp angle. The objective of this study was to establish a clinical scoring model to grade the technical difficulty of endoscopic resection for cardial SMTs.
A total of 246 patients who suffered cardial SMTs and received endoscopic resection were included in this retrospective study. All of them were randomized into the training cohort (n = 123) or internal validation cohort (n = 123). Potential predictors were analyzed using univariate analysis. Then, covariates with P < 0.05 were selected for the multivariate logistic regression model. The β coefficients from the logistic regression model were used to create a scoring system for technical difficulty prediction by rounding the score to the nearest integer of the absolute β coefficient value.
The clinical score consisted of the following factors: male gender (2 points), extraluminal growth (3 points), and maximum diameter ≥3 cm (3 points). The scoring model demonstrated good discriminatory power, with an area under the receiver operating characteristic curve of 0.860 and a 95% confidence interval of 0.763-0.958. The model also showed a good goodness of fit in the Hosmer-Lemeshow test (P = 0.979). In the training cohort, the probability of encountering technical difficulty in the easy (score = 0), intermediate (score = 1-3), difficult (score = 4-6), and very difficult (score >6) categories was 0, 6.8%, 33.3%, and 100.0%, respectively; similarly, in the validation cohort, it was 0, 5.6%, 22.2%, and 50.0%, respectively.
This scoring system could serve as a valuable tool for clinicians in predicting the technical difficulty of endoscopic resection for cardial SMTs.
This article presents a novel circularly polarized (CP) antenna based on an anisotropic metamaterial. The antenna is capable of performing linear-to-circular polarization conversion over a wideband ...of frequencies in the X-band (8-12 GHz). The proposed antenna was constructed from a metamaterial-based polarizer mounted above the aperture of a rectangular waveguide. The polarizer was oriented at 45° to E-plane of the waveguide. The proposed polarizer is composed of multiple metamaterial layers. The unit cell of the proposed polarizer consists of a single dielectric slab incorporating a series of rectangular split ring resonators that are printed on both sides of the slab. Impedance matching layers (IML) are introduced to enhance the axial-ratio (AR) bandwidth. The polarizer has a low profile in terms of electrical length (thickness of <inline-formula> <tex-math notation="LaTeX">0.41 \lambda _{0} </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">\lambda _{0} </tex-math></inline-formula> is the free-space wavelength at 10.5 GHz). A full-wave electromagnetic simulator was used to verify the anisotropic characteristics of the unit cell. This was achieved by showing that the metamaterial exhibits two different refractive indices along the orthogonal components of the incident electric field. The prototype of the proposed design is fabricated and measured to validate the performance. The measured results agree with the simulated ones and demonstrated a wide impedance bandwidth of 62.4% ranging from 7.08 to 13.5 GHz with a 3 dB AR bandwidth of 29.9% (9.25-12.5 GHz).
This paper proposes a novel mean-field matrix-analytic method in the study of bike sharing systems, in which a Markovian environment is constructed to express time-inhomogeneity and asymmetry of ...processes that customers rent and return bikes. To achieve effective computability of this mean-field method, this study provides a unified framework through the following three basic steps. The first one is to deal with a major challenge encountered in setting up mean-field block-structured equations in general bike sharing systems. Accordingly, we provide an effective technique to establish a necessary reference system, which is a time-inhomogeneous queue with block structures. The second one is to prove asymptotic independence (or propagation of chaos) in terms of martingale limits. Note that asymptotic independence ensures and supports that we can construct a nonlinear quasi-birth-and-death (QBD) process, such that the stationary probability of problematic stations can be computed under a unified nonlinear QBD framework. Lastly, in the third step, we use some numerical examples to show the effectiveness and computability of the mean-field matrix-analytic method, and also to provide valuable observation of the influence of some key parameters on system performance. We are optimistic that the methodology and results given in this paper are applicable in the study of general large-scale bike sharing systems.
•Solid digestate (SD) is a potential feedstock for preparing biochars.•The optimal BET surface area of resulting biochar from SD is over 100m2/g.•The higher temperature leads to the increase in true ...density of resulting biochar, but exhibited a decreased higher heating value.•The SD-based biochar may be used as a biofertilizer due to the mesoporosity and the abundant in nutrient minerals.
In the study, the biogas digestate was evaluated as a potential feedstock for preparing biochars at a broad temperature range of 300–900°C. The physico-chemical and pore properties of the resulting biochars (denoted as SDBC, solid digestate biochar), including calorific value (higher heating value), surface area/pore volume/pore size distribution, true density, scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray powder diffraction (XRD), were studied. It was found that the higher heating values of the SDBC products were on a decreasing trend as pyrolysis temperature increased, but they indicated an increase in true density. The results are probably associated with the active pyrolysis of the lignocellulosic fragments and the calcination (or shrinkage) processes, thus resulting in the increased contents of aromatic carbon clusters and main mineral constituents remained. Based on the pore properties, pyrolysis temperature at around 800°C seemed to be the optimal condition for producing SDBC, where its Brunauer-Emmet-Teller (BET) surface area (>100m2/g) largely increased as compared to that of the digestate feedstock (<1m2/g). Furthermore, the main compositions of mineral ash in the resulting biochar could exist as phosphates, carbonates, or oxides of calcium and other alkali/alkaline earth elements. According to the data on EDS and XRD, more pores could be significantly generated under severe pyrolysis (>700°C) due to the high aromaticity via the thermal decomposition of lignocelluloses and the volatilization of inorganic minerals.
In this paper, we develop the matrix-analytic method to discuss an interesting but challenging bilateral stochastic matching problem: A matched queue with matching batch pair (m,n) and two types of ...impatient customers, where the two types of customers arrive according to two independent Poisson processes. Once m A-customers and n B-customers are matched as a group, the m+n customers immediately leave the system. We show that this matched queue can be expressed as a novel bidirectional level-dependent quasi-birth-and-death (QBD) process whose analysis has its own interests, and specifically, computing the maximal non-positive inverse matrices of bidirectional infinite sizes by using the RG-factorizations. Based on this, we can provide an effective matrix-analytic method to deal with this matched queue, including the system stability, the average stationary queue lengths, the average sojourn times, and the departure process. We believe that the methodology and results developed in this paper can be applicable to studying more general matched queueing systems, which are widely encountered in many practical areas.
•Propose a two-stage stochastic optimization model.•Jointly optimize pre- and post-disaster planning for restoration tasks.•Explicitly consider two layers of interdependent infrastructures.•Propose ...an efficient Lagrangian Relaxation algorithm.
Pre-disaster planning and post-disaster scheduling are common strategies to increase the resilience of critical infrastructure. In this paper, we propose a new two-stage stochastic optimization model to simultaneously determine the locations for building stations of restoration teams before disasters and their routing of conducting restoration tasks after disasters. Two layers of interdependent infrastructures are explicitly considered in the proposed model: The first layer for the transmission of flows to satisfy customers’ demands (e.g., a power transmission or telecommunication network) and the second layer for the transportation of restoration crews (i.e., the transportation nework). We seek to minimize the total cost, including the station building cost and the penalty cost incurred by performance loss. To deal with the computational complexity of the proposed problem, we propose a Column-generation-based Lagrangian Relaxation algorithm with a dynamic programming algorithm embedded to solve the included pricing problem. Extensive computational experiments, including the real-world infrastructures (i.e., French natural gas network), are conducted to illustrate the merits of the proposed approach.
Abstract The in vivo endothelialisation of materials provides a promising strategy for the rapid re-endothelialisation of a cardiovascular implantation. Although many studies have focused on ...improving the rapid endothelialisation through the immobilisation of bioactive molecules, it should be noted that the endothelial cells (ECs) will compete with other cell types in vivo . Thus, the efforts to partially enhance the EC growth without considering the cell competition might be misleading and meaningless in vivo . In this study, we demonstrated that the competitive growth of human umbilical vein endothelial cells (HUVECs) over human aortic smooth muscle cells (HASMCs) could be increased through the synergic action of the nonspecific resistance to phosphorylcholine and the specific recognition of the REDV peptide. Further in vivo data indicate that the competitive ability of ECs over SMCs, instead of the number of ECs, is a significantly more important criterion for the development of a pure endothelial layer in vivo and thus the attainment of a better anti-restenosis effect. Consequently, the surface tailoring of a stent to obtain high endothelial cell selectivity is likely an effective design criterion for in situ endothelialisation and a possible future solution for the problem of in-stent restenosis.
PDF
