On the uniqueness of semi-wavefronts for non-local delayed reaction–diffusion equations

We establish the uniqueness of semi-wavefront solution for a non-local delayed reaction–diffusion equation. This result is obtained by using a generalization of the Diekmann–Kaper theory for a nonlinear convolution equation. Several applications to the systems of non-local reaction–diffusion equations with distributed time delay are also considered.     

Determination of macrolides in livestock excreta by syringe purification coupled with liquid chromatography tandem mass spectrometryEI北大核心CSCD

A method of syringe-dispersive solid-phase extraction combined with ultrahigh performance liquid chromatography with tandem mass spectrometry for the simultanous determination of 10 macrolides in manurebased fertilizers was developed. After extraction with methanol and acetonitrile,the extracts were purified by insyringe dispersion solid-phase extraction in syringes pre-filled with 60 mg PSA and 30 mg C18. The resulted extracts were further separated by a BEH C18 column,detected by multiple reaction monitoring in electrospray positive ion mode,and quantified by matrix-matched external standard method. The results showed that the recoveries of the target compounds ranged from 70% to 110% at three spiked levels（10,30,and 50 μµg/kg）with the relative standard deviations ranged from 1.4% to 12%. The limits of detection and quantification were 0.57 1.75 and 2.77-5.40 μµg/kg,respectively. This method was suitable for the simultaneous determination of residual macrolides in organic fertilizers. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

亲水头基大小对正负离子表面活性剂混合体系的影响

<正>负离子表面活性剂混合体系曾被认为是表面活性剂配方的禁忌,但通过增大表面活性剂头基的面积,正负混合体系在很宽的物质的量比下都不会产生沉淀,而且还会产生显著的增效效应。头基大的离子型表面活性剂甚至能够用来增溶难溶的反电荷表面活性剂。     

具有高灵敏性且稳定可重复的正温度系数效应的PVDF/CF导电复合材料

以碳纤维(CF)为填料,聚偏氟乙烯(PVDF)为基体,通过熔融共混法制备PVDF/CF导电复合材料.所得复合材料具有显著的正温度系数(PTC)效应,温度上升到聚合物熔点附近时,电阻率对温度变化敏感.在转折温度区间(155.5~171.0oC,(35)(28)15.5oC)内,其体积电阻率的增加速率约为1.3×105?cm K-1.在不同CF含量下,复合材料表现出不同的PTC行为.随着CF含量的增加,其峰值电阻略有下降.高导电粒子含量下,无负温度系数(NTC)效应.在冷却循环过程,导电网络的重构性良好.复合材料即使经过多次热循环,依然表现出良好的PTC特性重现性.     

Contractivity results in ordered spaces. Applications to relative operator bounds and projections with norm one

This paper provides various “contractivity” results for linear operators of the form where C are positive contractions on real ordered Banach spaces X . If A generates a positive contraction semigroup in Lebesgue spaces , we show (M. Pierre's result) that is a “contraction on the positive cone ”, i.e. for all provided that .  We show also that this result is not true for 1 ⩽ . We give an extension of M. Pierre's result to general ordered Banach spaces X under a suitable uniform monotony assumption on the duality map on the positive cone . We deduce from this result that, in such spaces, is a contraction on for any positive projection C with norm 1. We give also a direct proof (by E. Ricard) of this last result if additionally the norm is smooth on the positive cone. For any positive contraction C on base‐norm spaces X (e.g. in real spaces or in preduals of hermitian part of von Neumann algebras), we show that for all where N is the canonical half‐norm in X . For any positive contraction C on order‐unit spaces X (e.g. on the hermitian part of a algebra), we show that is a contraction on . Applications to relative operator bounds, ergodic projections and conditional expectations are given.     

How do the positive embeddings of Banach lattices depend on the αth derivatives of K?

Let K and S be locally compact Hausdorff spaces and X be an abstract space. Suppose that T is a positive Banach lattice isomorphism from into . Then for each ordinal α the cardinalities of the αth derivatives and satisfy the following inequality Moreover, if then is a continuous image of a subset of which can be taken closed when K is compact. The first statement of this result for is a vector‐valued extension of a Cengiz's theorem and the second one is vector‐valued version of a Holsztyński's theorem. A simple example shows that the number is sharp in these vector‐valued theorems.     

Enhanced Reproducibility of Positive Temperature Coefficient Effect of CB/HDPE/PVDF Composites with the Addition of Ionic Liquid

Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC) effect is of great significance for large-scale application of polymer based PTC composites, owing to its contribution to the security and reliability. Herein, we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF) composite with outstanding PTC reproducibility, by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf_2]) into the composite. After multiple repeated temperature cycles, the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%. Our studies revealed that [OMIm][NTf2] contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii) it inhibits the crystallization of PVDF through the dilution effect, leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF. This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.     

Frobenius–Ehresmann structures and Cartan geometries in positive characteristic

The aim of the present paper is to lay the foundation for a theory of Ehresmann structures in positive characteristic, generalizing the Frobenius-projective and Frobenius-affine structures defined in the previous work. This theory deals with atlases of étale coordinate charts on varieties modeled on homogeneous spaces of algebraic groups, which we call Frobenius–Ehresmann structures. These structures are compared with Cartan geometries in positive characteristic, as well as with higher-dimensional generalizations of dormant indigenous bundles. In particular, we investigate the conditions under which these geometric structures are equivalent to each other. Also, we consider the classification problem of Frobenius–Ehresmann structures on algebraic curves. The latter half of the present paper discusses the deformation theory of indigenous bundles in the algebraic setting. The tangent and obstruction spaces of various deformation functors are computed in terms of the hypercohomology groups of certain complexes. As a consequence, we formulate and prove the Ehresmann–Weil–Thurston principle for Frobenius–Ehresmann structures. This fact asserts that deformations of a variety equipped with a Frobenius–Ehresmann structure are completely determined by their monodromy crystals.     

On reachable set bounding for discrete-time switched nonlinear positive systems with mixed time-varying delays and disturbance

This paper addresses the reachable set bounding for discrete-time switched nonlinear positive systems with mixed time-varying delays and disturbance, which contains switched linear positive systems as a special case. By resorting to a new method that does not involve the common Lyapunov–Krasovskii functional one, explicit criteria to ensure any state trajectory of the system converges exponentially into a prescribed sphere are obtained under average dwell time switching. The results can then be extended to more general time-varying systems. Finally, two numerical examples are used to demonstrate the effectiveness of the obtained results.