Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Nanocomposites constructed by combining mesoporous metal oxides and graphene have received tremendous attention in wide fields of catalysis,energy storage and conversion,gas sensing and so on.Herein,we present a facile interface-induced co-assembly process to synthesize the mesoporous W03@graphene aerogel nanocomposites(denoted as mW03@GA),in which graphene aerogel(GA) was used as a macroporous substrate,mesoporous W03 was uniformly coated on both sides of graphene sheets through a solvent evaporation-induced self-assembly(EISA) strategy using diblock copolymer poly(ethylene oxide)-b-polystyrene(PEO-b-PS) as a template.The resultant mW03@GA nanocomposites possess well-interconnected macroporous graphene networks covered by mesoporous W03 layer with a uniform pore size of 19 nm,high surface area of 167 m~2/g and large pore volume of 0.26 cm~3/g.The gas sensing performance of mW03@GA nanocomposites toward acetone and other gases was studied,showing a high selectivity and great response to acetone at low temperature of 150℃,which could be developed as a promising candidate as novel sensors for VOCs detection.     

Electronic and Optical Properties of KNbO3,NaNbO3 and K0.5 Na0.5 NbO3 in Paraelectric Cubic Phase：a Comparative First-principles Study

The structural,electronic and optical properties of KNbO 3 (KN),NaNbO3(NN)and K05 Na0.5NbO3(KNN) in paraelectric cubic phase were calculated employing the plane-wave pseudopotential method based on density functional theory (DFT).The calculated electronic structures of the three crystals show similar features in the valence bands and the lower conduction bands.However,the structures in higher conduction bands differ markedly due to the effect of Na and K atoms.The calculated optical properties reveal that the features of optical spectrum at low energy are dominated by the transitions from O2p valence bands to Nb 4d conduction bands and those at high energy are related to the transitions to K 4s4p and/or Na 3s3p states.Moreover,the optical constants of KNN are approximately the average of KN and NN at high energy.Therefore,the optical properties of KNN in high energy region can probably be altered by changing the ratio of Na/K.     

Enhancement of corrosion resistance of electrocodeposited Ni–SiC composites by magnetic field

The corrosion behavior and surface morphology of Ni–SiC composite coatings produced by electrodeposition with the aid of magnetic field were studied. The results of the electrochemical analysis including polarization resistance and potentiodynamic polarization curves showed that a magnetic field of 0.1 T could significantly improve the corrosion resistance of the composite. The electrochemical impedance spectra revealed that a passive layer was formed on the surface of the Ni–SiC coating with the magnetic field. The microstructures of electrodeposited Ni–SiC composite coatings were also examined. More SiC particles were found to be incorporated into the coating with the presence of magnetic field, which was considered to be one of the reasons for the enhancement of corrosion resistance as SiC particles were reported to be corrosion inhibitors. Contribution to special issue “Magnetic field effects in Electrochemistry”     

TiO<Subscript>2</Subscript> Nanorod Arrays Sensitized with CdS Quantum Dots for Solar Cell Applications: Effects of Rod Geometry on Photoelectrochemical Performance

CdS quantum dot (QD) sensitized TiO₂ nanorod array (NRA) film electrodes with different rod geometries were fabricated via a solvothermal route followed by a sequentialchemical bath deposition (S-CBD) process. By controlling the solution growth conditions, the rod geometries, especially the tip structures, of the TiO₂ NRAs were tuned. The results indicated that the vertically aligned hierarchical NRAs possessed conically shaped tip geometry, which was favorable for film electrodes due to the reduced reflectance, enhanced light harvesting, fast charge-carrier separation and transfer, suppression of carrier recombination, sufficient electrolyte penetration and subsequent efficient QD assembly. CdS QD sensitized TiO₂ NRA film electrodes with tapered tips exhibited an enhanced photoelectrochemical (PEC) performance, a photocurrent intensity of 5.13 mA/cm² at a potential of 0 V vs. saturated calomel electrode, an open-circuit potential of −0.68 V vs. saturated calomel electrode and an incident photon to current conversion efficiency (IPCE) of 22% in the visible-light region from 400 to 500 nm. The effects of rod geometry on the optical absorption, reflectance, hydrophilic properties and PEC performance of bare TiO₂ and CdS QD sensitized TiO₂ NRA film electrodes were investigated. The mechanism of charge-carrier generation and transfer in these CdS QD sensitized solar cells based on vertically aligned TiO₂ nanorods is discussed.     

Optimal investment with transaction costs based on exponential utility function: a parabolic double obstacle problem

This paper concerns optimal investment problem with proportional transaction costs and finite time horizon based on exponential utility function. Using a partial differential equation approach, we reveal that the problem is equivalent to a parabolic double obstacle problem involving two free boundaries that correspond to the optimal buying and selling policies. Numerical examples are obtained by the binomial method.     

部分服务台异步单重休假M/M/c排队

利用拟生灭过程和矩阵几何解的方法研究了只允许部分服务台异步单重休假的M/M/c排队系统,给出了系统的稳态指标的计算方法和条件随机分解结果,最后指出一些较简单的排队模型是本文的特例.     

严格循环的算子代数

设X是半自共轭的Banach空间,而A是B(X)的严格循环的交换子代数,考虑算子代数A的一些性质,这些性质与算子代数的自反性有关,而且这些性质为讨论A的自反性提供了理论基础.     

位置参数估计量的损失函数之估计

本文考虑损失函数的估计问题,分别对于球对称分布和均匀分布情形给出了其参数的J-S型估计量的损失之估计,它们满足[1]中提出的条件(Ⅰ)和(Ⅱ).