Unconditionally optimal convergence of an energy-conserving and linearly implicit scheme for nonlinear wave equations

In this paper, we present and analyze an energy-conserving and linearly implicit scheme for solving the nonlinear wave equations. Optimal error estimates in time and superconvergent error estimates in space are established without certain time-step restrictions. The key is to estimate directly the solution bounds in the H²-norm for both the nonlinear wave equation and the corresponding fully discrete scheme, while the previous investigations rely on the temporal-spatial error splitting approach. Numerical examples are presented to confirm energy-conserving properties, unconditional convergence and optimal error estimates, respectively, of the proposed fully discrete schemes.

     

Restructuring and Activation of Cu(111) under Electrocatalytic Reduction Conditions

The dynamic restructuring of Cu surfaces in electroreduction conditions is of fundamental interest in electrocatalysis. We decode the structural dynamics of a Cu(111) electrode under reduction conditions by joint first-principles calculations and operando electrochemical scanning tunneling microscopy (ECSTM) experiments. Combining global optimization and grand canonical density functional theory, we unravel the potential- and pH-dependent restructuring of Cu(111) in acidic electrolyte. At reductive potential, Cu(111) is covered by a high density of H atoms and, below a threshold potential, Cu adatoms are formed on the surface in a (4×4) superstructure, a restructuring unfavorable in vacuum. The strong H adsorption is the driving force for the restructuring, itself induced by the electrode potential. On the restructured surface, barriers for hydrogen evolution reaction steps are low. Restructuring in electroreduction conditions creates highly active Cu adatom sites not present on Cu(111).     

One‐pot Synthesis of 2,5‐Disubstituted‐1,3,4‐oxadiazoles Based on the Reaction of N,N‐Dimethyl Amides with Acid Hydrazides

Convenient and efficient one pot method for the synthesis of 2,5‐disubstituted‐1,3,4‐oxadiazoles based on the reaction of N,N‐dimethyl amides with acid hydrazides has been developed. The methodology is applied to a wide range of difference aryl hydrazide and difference N,N‐dimethyl amides to 2,5‐disubstituted‐1,3,4‐oxadiazoles yield the in good to excellent yields. It will be possible wide useful application in synthesis.     

Heterostructural BiOI/TiO2 composite with highly enhanced visible light photocatalytic performance

Binary BiOI/TiO₂ hybrid material was synthesized via a sol-gel method combined with chemical etching. The as-prepared powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PLS) and photocurrent response tests. Under visible light (λ > 420 nm), BiOI/TiO₂ degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure BiOI. Moreover, BiOI/TiO₂ can effectively promote photooxidation of other organic dyes like rhodamine B (RhB), crystal violet (CV) and methylene blue (MB). In addition, the quenching effects of different scavengers proved that reactive O ₂ ^? and h⁺ played the major role in the MO degradation. The photocatalytic activity enhancement of BiOI/TiO₂ is closely related to the strong absorption in the visible region, and the efficient charge separation derived from the matching band potentials between BiOI and TiO₂, as well as the low recombination rate of the electron-hole pairs due to the heterojunction formed between BiOI and TiO₂.     

稀土钼酸2-氨基-4,6-二甲氧基嘧啶三元配合物的合成、表征及其生物活性研究

以稀土氯化物、钼酸钠和2-氨基-4,6-二甲氧基嘧啶为原料,制备了一类新型稀土三元配合物,通过元素分析、红外光谱、紫外光谱、热重-差热分析、透射电子显微镜及X射线粉末衍射等手段对配合物进行了表征,确定了该类配合物的化学组成为:RE3(ADP)(MoO4)2(CH3OH)4Cl5·2H2O(RE=La3+,Sm3+,Y3+,Er3+,ADP=2-氨基-4,6-二甲氧基嘧啶).抗菌实验结果表明,稀土三元配合物对大肠杆菌、金黄色葡萄球菌具有较强的抑制作用,属于广谱抗菌剂.用四甲基偶氮唑蓝微量酶反应比色法(MTT)法初步研究了三元配合物的抗癌能力,结果证明其具有使癌细胞凋亡的效果.     

Ionic liquid promoted preparation of 4H-thiopyran and pyrimidine nucleoside-thiopyran hybrids through one-pot multi-component reaction of thioamide

One-pot multi-component reactions of aldehydes, cyanothioacetamide and malononitrile promoted by ionic liquid proved to be an efficient way for the synthesis of thiopyran derivatives. Without any added catalyst, both aromatic and aliphatic aldehydes participated in this reaction smoothly. As an application of this method, a pyrimidine nucleoside-thiopyran chimera with potential biological activities was obtained in high yield from 5-formyl-2’-deoxyuridine. In addition, the ionic liquid used can be easily recovered and effectively reused for at least 5 times. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

SUPERCONVERGENCE OF A DISCONTINUOUS GALERKIN METHOD FOR FIRST-ORDER LINEAR DELAY DIFFERENTIAL EQUATIONS

This paper deals with the discontinuous Galerkin (DG) methods for delay differential equations.By an orthogonal analysis in each element,the superconvergence re...     

Studies on the effects of nonadiabatic behavior during the course of HBr photolysis

From quantum mechanical simulation, photodissociation of hydrogen bromide (HBr) in its first UV absorption continuum (A band) taking place upon excitation has been studied. The absorbencies are inferred from techniques of Forurier transformation. On that foundation, the branching fractions for the spin-excited Br* (²P_1/2) channel at enormous photon frequencies are gained. Moreover, the relevant MOs have been analyzed to obtain more information about the dissociation process within the framework of the time-dependent density functional theory. The results unravel that the possibility of intersystem crossing does exist in the photodissociation course, which involve the coupling of the a³Π₀ ⁺ and A¹Π₁ potential surfaces. The prediction of the wavelength dependence of the anisotropy parameter β agrees with the experiment within a major part of A band, which provides an insight into the reaction dynamics and the transiton probability is conjectured to be larger when channels approach each other, notwithstanding a steady decline towards the red wing of spectrum.     

Improved visible light photocatalytic activity of titania loaded with silver on discoloration of a heterocyclic aromatic chemical dye solution

The photocatalytic activity of silver deposited Degussa P25 titanium dioxide (Ag-DP25) in the photodegradation of methylene blue (MB) was investigated. The as-prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), infrared spectra and surface photovoltage spectroscopy (SPS) techniques. The obtained results show that the silver dopant could effectively inhibit the recombination of the photoinduced electron and holes, improving the absorption capability for visible light of photocatalyst and leading to increased surface OH group density. The degradation experiment reveals that the catalytic property of Ag-DP25 in the degradation of MB dye is more efficient than that of commercially available Degussa P25 TiO₂ (DP25) samples under visible-light irradiation. Besides, degradation kinetics of MB dye can, be well described by Langmuir-Hinshelwood equation and shows pseudo-first order law.     

Some notes on split Newton iterative algorithm

In this study, a parameterized split Newton method is derived by using the accelerating technique. Convergence and error estimates of the method are obtained. In practical application, the proposed method can give a better result in view of computational CPU time. Numerical examples on several partial differential equations are shown to illustrate our findings. Copyright © 2015 John Wiley & Sons, Ltd.