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The effects of KBrO3 modification on polyacrylonitrile (PAN) precursor fibers at different modification temperatures were studied. The mechanical properties, chemical structure, aggregation structure, morphological structure, and thermal behavior of PAN precursor fibers were analyzed. The mechanical properties of PAN precursor fibers are essentially unaltered after KBrO3 modification, although oxygen-containing functional groups are introduced. KBrO3 can ionize bromate ion in aqueous solution, which has good nucleophilicity and can attack the positively charged carbon atom in C≡N, so that the cyclization proceeds according to the ionic mechanism, allowing the transformation of C≡N to C = N in the PAN precursor fibers generated a cyclic trapezoidal structure containing primary aromatic amine, which reduced the peak temperature of the cyclization reaction from 284.5 °C to 275.1 °C and decreased the heat release. The sp3-hybridized carbon structure changes into a sp2 hybridized C = C structure with increasing aromatization, according to XRD and Raman data, and the KBrO3 alteration accelerates the degradation of the original microcrystalline structure and transforms into a new polycyclic aromatic structure. The degree of conjugation and aromatization of the system rapidly increased with the rise in modification temperature. The stabilized fibers were discovered to have the lowest R-value, the highest aromatization, the smoothest surface, and the fewest flaws at impregnation temperature of 60 °C. [ABSTRACT FROM AUTHOR]

In Zhu et al. (SIAM J Sci Comput 43: A3009–A3031, 2021), we proposed a new framework of troubled-cell indicator (TCI) using K-means clustering for the discontinuous Galerkin (DG) methods. However, there are two user-tunable parameters in the framework that depend on the polynomial degree of the solution space, the indication variable and even the test problem, which circumscribe the application of the framework. To overcome this drawback, we introduce two simple techniques in this paper: one is to modify the indication variables and the other is to apply a statistical normalization to the modified values. Coupled with four different indication variables, the modified framework is tested via the classical benchmark problems and produces close results under the same setting of the parameters. The discontinuities are overall well captured and the solutions are free of spurious oscillations. The numerical results demonstrate the effectiveness and flexibility of the modified framework and the success in unifying the parameters. Existing TCIs/limiters for the DG methods can be easily implemented into this framework. [ABSTRACT FROM AUTHOR]

In this work, we study the strong decay of the newly observed Pcs(4459), assuming that it is a pure molecular state. Considering two possible spin-parity assignments JP = 1/2− and JP = 3/2−, the partial decay widths of the molecular state into J/ψΛ, Ds−Λc+, and final states through hadronic loops are evaluated with the help of the effective Lagrangians. In comparison with the LHCb data, the S-wave molecular with JP = 1/2− assignment for Pcs(4459) is supported by our study, while the Pcs(4459) in spin-parity JP = 3/2− case may be explained as an S-wave coupled bound state with lager component. In addition, the calculated partial decay widths with JP = 1/2− molecular state picture indicate that allowed decay mode, , may have the biggest branching ratio. The experimental measurements for this strong decay process could be a crucial test for the molecule interpretation of the Pcs(4459). [ABSTRACT FROM AUTHOR]

Very recently, three new structures Ξ c (2923) 0 , Ξ c (2938) 0 , and Ξ c (2964) 0 at the invariant mass spectrum of Λ c + K - observed by the LHCb Collaboration trigger a hot discussion about their inner structure. In this work, we study the strong decay mode of the newly observed Ξ c 0 assuming that the Ξ c 0 is a D ¯ Λ - D ¯ Σ molecular state. With the possible quantum numbers J p = 1 / 2 ± and 3 / 2 ± , the partial decay widths of the D ¯ Λ - D ¯ Σ molecular state into the Λ c + K - , Σ c + K - ,and Ξ c + π - final states through hadronic loop are calculated with the help of the effective Lagrangians. By comparison with the LHCb observation, the current results of total decay width support the Ξ c (2923) 0 as D ¯ Λ - D ¯ Σ molecule while the decay width of the Ξ c (2938) 0 and Ξ c (2964) 0 can not be well reproduced in the molecular state picture. In addition, the calculated partial decay widths with S wave D ¯ Λ - D ¯ Σ molecular state picture indicate that allowed decay mode, Ξ c + π - , may have the biggest branching ratio for the Ξ c (2923) 0 . The experimental measurements for this strong decay process could be a crucial test for the molecule interpretation of the Ξ c (2923) 0 . [ABSTRACT FROM AUTHOR]

In this paper, we generalize an h-adaptive Runge-Kutta discontinuous Galerkin scheme developed earlier in Zhu et al. (J Sci Comput 69:1346-1365, 2016) for the 1D Vlasov-Poisson system to the guiding center Vlasov model and the 2D time dependent incompressible Euler equations in the vorticity-stream function formulation. The main difficulty of this generalization lies in solving the 2D Poisson equation due to the irregular adaptive mesh with hanging nodes. We adopt a local discontinuous Galerkin method to solve the Poisson equation. The full adaptive algorithm and the related numerical implementation details are included. Extensive numerical tests have been performed to showcase the effectiveness of the adaptive scheme and its advantage over the fixed-mesh scheme in saving computational cost and improving solution quality. [ABSTRACT FROM AUTHOR]

In this work, we discuss an extension of the adaptive technique in Zhu and Qiu (J. Comput. Phys. 228, 6957-6976 2009) to design an h-adaptive Runge-Kutta discontinuous Galerkin (RKDG) method for the simulations of several classical one-dimensional detonation waves. The TVB troubled-cell indicator is employed to detect the troubled cells which are believed to contain the discontinuities. An adaptive mesh is generated at each time-level by refining the troubled cells and coarsening the others. A recursive multi-level mesh refinement technique is designed to avoid the problem that the detonation front moves so fast that there are not enough cells to resolve the detonation front before it leaves. We describe the numerical implementation in detail including the adaptive procedure, solution reconstruction method and troubled-cell indicator. Furthermore, a high order positivity-preserving technique is employed for the robustness of our algorithm. Extensive numerical tests are conducted to show the effectiveness of the adaptive strategy and advantages of our adaptive method over the fixed-mesh RKDG method in saving the computational storage and improving the solution quality. [ABSTRACT FROM AUTHOR]

The first account of the effects of wetland reclamation on soil nematode assemblages were provided, three sites in Heihe River Basin of Northwest China, that is grass wetland (GW), Tamarix chinensis wetland (TW) and crop wetland (CW) treatments, were compared. Results showed that the majority of soil nematodes were presented in the 0-20 cm soil layers in CW treatments, followed by in the 20-40 cm and 40-60 cm layers in GW treatments. Plant-feeding nametodes were the most abundant trophic groups in each treatment, where GW (91.0%) > TW (88.1%) > CW (53.5%). Generic richness (GR) was lower in the TW (16) than that in GW (23) and CW (25). The combination of enrichment index (EI) and structure index (SI) showed that the soil food web in GW was more structured, and those in TW was stressed, while the enrichment soil food web was presented in the CW treatment. Several ecological indices which reflected soil community structure, diversity, Shannon-Weaver diversity (H′), Evenness (J′), Richness (GR) and modified maturity index (MMI) were found to be effective for assessing the response of soil namatode communities to soil of saline wetland reclamation. Furthermore, saline wetland reclamation also exerted great influence on the soil physical and chemical properties (pH, Electric conductivity (EC), Total organic carbon (TOC), Total nitrogen (Total-N) and Nitrate Nitrogen (N-NO)). These results indicated that the wetland reclamation had significantly effects on soil nematode community structure and soil properties in this study. [ABSTRACT FROM AUTHOR]

In Zhu and Qiu (J Comput Phys 228:6957-6976, ), we systematically investigated adaptive Runge-Kutta discontinuous Galerkin (RKDG) methods for hyperbolic conservation laws with different indicators, with an objective of obtaining efficient and reliable indicators to obtain better performance for adaptive computation to save computational cost. In this follow-up paper, we extend the method to solve two-dimensional problems. Although the main idea of the method for two-dimensional case is similar to that for one-dimensional case, the extension of the implementation of the method to two-dimensional case is nontrivial because of the complexity of the adaptive mesh with hanging nodes. We lay our emphasis on the implementation details including adaptive procedure, solution projection, solution reconstruction and troubled-cell indicator. Extensive numerical experiments are presented to show the effectiveness of the method. [ABSTRACT FROM AUTHOR]