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51.
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Let K and S be locally compact Hausdorff spaces and let X be a strictly convex Banach space of finite dimension at least 2. In this paper, we prove that if there exists an isomorphism T from onto satisfying then K and S are homeomorphic. Here denotes the Schäffer constant of X. Even for the classical cases , and , this result is the X‐valued Banach–Stone theorem via isomorphism with the largest distortion that is known so far, namely . On the other hand, it is well known that this result is not true for , even though K and S are compact Hausdorff spaces. 相似文献
54.
This paper develops a framework to deal with the unconditional superclose analysis of
nonlinear parabolic equation. Taking the finite element pair $Q_{11}/Q_{01} × Q_{10}$ as an example,
a new mixed finite element method (FEM) is established and the $τ$ -independent superclose
results of the original variable $u$ in $H^1$-norm and the flux variable $\mathop{q} \limits ^{\rightarrow}= −a(u)∇u$ in $L^2$-norm are deduced ($τ$ is the temporal partition parameter). A key to our analysis is an
error splitting technique, with which the time-discrete and the spatial-discrete systems are
constructed, respectively. For the first system, the boundedness of the temporal errors is obtained. For the second system, the spatial superclose results are presented unconditionally, while the previous literature always only obtain the convergent estimates or require
certain time step conditions. Finally, some numerical results are provided to confirm the
theoretical analysis, and show the efficiency of the proposed method. 相似文献
55.
Wen‐ming He 《Numerical Methods for Partial Differential Equations》2019,35(6):2044-2055
In this article, we will discuss the local ultraconvergence of high‐degree finite element method based on a rectangular partition for the second‐degree elliptic problem with constant coefficients in Ω ? ?2 , u( y ) = 0 on ?Ω . Based on suitable regularity, ultraconvergence of the displacement of the extrapolated kth (k ≥ 3) degree finite element solution has been obtained by an extrapolation technique. Finally, numerical experiments are applied to demonstrate our theoretical findings. 相似文献
56.
57.
Mahmoud Nasrollahzadeh Mohaddeseh Sajjadi Hartmut Komber Hossein Ali Khonakdar S. Mohammad Sajadi 《应用有机金属化学》2019,33(7)
In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu2+ and Ni2+ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN3. 相似文献
58.
Josué M. Silla Laize A.F. Andrade Matheus P. Freitas 《Magnetic resonance in chemistry : MRC》2019,57(7):373-379
The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C─H (C─F for the fluorine Perlin-like effect) spin–spin coupling constants (SSCCs) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C─H and C─F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects, and induced current density. Accordingly, a variety of model compounds has been used to probe such effects since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects. Thus, the 1JC─F SSCC in fluorinated lactams and lactones were theoretically studied to gain further insight on the nature of the fluorine Perlin-like effect. In addition, because the intramolecular α-effect has recently gained attention for its importance in the reactivity and stereoelectronic interactions in peroxide compounds, some fluorinated 1,2-dioxanes and 1,2-dithianes were studied to evaluate the role of the α-effect on the behavior of 1JC─F SSCCs. Differently from fluorinated ketones and ethers, the fluorine Perlin-like effect in the amides and esters cannot be explained by hyperconjugative or dipolar interactions alone, because the resonance in these groups affect the 1JC─F values. The O─O and S─S-containing systems exhibit a strong fluorine Perlin-like effect, but unlike the α-effect, this behavior cannot be explained neither by hyperconjugation nor by dipolar interactions alone; the spatial proximity of the C─F and O─O/S─S bonds is proposed to affect the magnitude of the 1JC─F SSCC. 相似文献
59.
60.
Johisner Penagos‐Llanos Olimpo García‐Beltrn J. A. Caldern Edgar Nagles J. J. Hurtado 《Electroanalysis》2019,31(4):695-703
The detection of Allura red (AR) by electrochemical reduction using a different electrode from the conventional mercury electrode is presented. A carbon paste with cobalt (II, III) oxide composite electrode (CoOx/CPE) is reported for the first time for the detection of AR. Moreover, others dyes such as tartrazine (TZ), sunset yellow (SY), amaranth (AM), Ponceaut 4‐R (P‐4R), and Sudan (SD) as well as pharmaceutical agents such as paracetamol (PMC) that are present in samples that contained AR did not show a reduced signal between 0.0 and ?0.3 V, which is the potential range where AR reduction was observed. The surface electroactivity was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of CoOX increased the cathodic peak current for AR by more than 50 % and 65 % via CV and square wave voltammetry (SWV), respectively, compared with an unmodified carbon paste electrode. Under the optimal parameters, (pH=3.0, accumulation time (tACC)=60 s and accumulation potential (EACC)=0.50 V), the detection limit for AR was 0.05 μmol L?1. The new sensor was sensitive and stable for the detection of AR. Moreover, it was easily manufactured and very convenient for food samples such as soft and isotonic drinks as well as chili sauce. 相似文献