The concept of dual roles design in clean organic preparation

Herein we summarized some clean preparation examples to emphasize the concept of dual roles design (or named as “two birds one stone strategy”) in green and sustainable chemistry. In those examples, the reactants and/or solvent play dual roles rendering a cleaner organic preparation process. Consequently, both the chemical waste and manufacturing cost could be reduced.     

Electrochemical synthesis of α,α-dihaloacetophenones from terminal alkyne derivatives

By virtue of electrochemistry, a series of α,α-dihaloacetophenones were easily obtained with good to excellent yields. This electrochemical procedure was taken in a divided cell with constant current in aqueous media. The reaction can be carried out smoothly at room temperature under metal and oxidant free condition, which provides an eco-friendly synthesis for the α,α-dihaloacetophenone derivatives.     

Oxidation of aromatic sulfides with molecular oxygen: Controllable synthesis of sulfoxides or sulfones

The recent development of selective oxidation of aromatic sulfides with molecular oxygen was highlighted. The sulfoxides and sulfones could be obtained by simply switching the reaction media, i.e., bis(2-butoxyethyl)ether (BBE) or poly(ethylene glycol)dimethyl ether (PEGDME). The application of the high-boiling-point polyether as an initiator and green media can eliminate the need of large quantities of additives and volatile solvents. This strategy represents an economic and eco-friendly method that could find potential applications.     

First-principles study on the electronic transport properties of M/SiC Schottky junctions (M=Ag,Au and Pd)

In this work, we investigate the electronic transport properties of M/SiC Schottky junctions (M=Ag, Au and Pd). The results show that the band structures of hydrogenated zigzag SiC nanoribbons (ZSiCNRs) and hydrogenated armchair SiC nanoribbons (ASiCNRs) are almost unaffected by their width changes. When the hydrogenated 7-ASiCNR is directly connected to the Ag, Au and Pd electrode, the transmission spectra of three metal-semiconductor junctions show that the Fermi level of metal is pinned to a fixed position in the semiconductor band gap of hydrogenated 7-ASiCNR. The nearly same rectifying current-voltage characteristics are found in three metal-semiconductor junctions. The average rectification ratios of three M/SiC Schottky junctions are all in the neighborhood of 10⁶. In other word, the M/SiC Schottky junction has remarkable application prospect as the candidate for Schottky Diode.     

Tunable electronic and optical properties of SnC/BAs heterostructure by external electric field and vertical strain

Based on the first-principles method, we investigate the electronic structure of SnC/BAs van der Waals (vdW) heterostructure and find that it has an intrinsic type-II band alignment with a direct band gap of 0.22 eV, which favors the separation of photogenerated electron–hole pairs. The band gap can be effectively modulated by applying vertical strain and external electric field, displaying a large alteration of band gap via the strain and experiencing an indirect-to-direct band gap transition. Moreover, the band gap of the heterostructure varies almost linearly with external electric field, and the semiconductor-to-metal transition can be realized in the presence of a strong electric field. The calculated band alignment and the optical absorption reveal that the SnC/BAs heterostructure could present an excellent light-harvesting performance. Our designed heterostructure is expected to have great potential applications in nanoelectronic devices and photovoltaics and optical properties.     

Swimming of micro-organism over an oscillatory stretched surface filled with a magnetic third-grade nanofluid: An application of activation energy

During the past few years, abundant involvement of nanoparticles in improving the thermal extrusion systems and energy resources attracted the attention of numerous scientists recently. The significance of nanofluid in terms of working liquid directed for the enhancement of solar energy and thermal extrusion performances. Therefore, the present analysis deals with the thermal performances of bioconvection flow with nanoparticles suspended in a non-Newtonian fluid. Considering that the flow has been induced due to periodically accelerated surface. The activation energy consequences are also employed in the concentration equation. The flow problem is initially formulated in the form of partial differential equations. The dimensionless variables are reported to renovate such equations in the dimensionless style, which are tackled analytically by employing the homotopy analysis method. The significance of various physical parameters is estimated for the relevant distribution of velocity, temperature, concentration, and motile micro-organisms. The dimensionless local Nusselt number, local Sherwood number, and motile density number are numerically iterated via flow parameters. A convergence analysis is also presented. The detected observation can involve theoretical significance in various engineering processes, bio-fuel cells, solar energy systems, and enhancement of extrusion systems.     

Bifurcations and dynamics of a plant disease system under non-smooth control strategy

Nonlinear Dynamics - Mathematical models and analyses can assist in designing the control strategies to prevent the spread of infectious disease. The present paper investigates the bifurcations and...     

Probabilities of incidence between lines and a plane curve over finite fields

We study the probability for a random line to intersect a given plane curve, over a finite field, in a given number of points over the same field. In particular, we focus on the limits of these probabilities under successive finite field extensions. Supposing absolute irreducibility for the curve, we show how a variant of the Chebotarev density theorem for function fields can be used to prove the existence of these limits, and to compute them under a mildly stronger condition, known as simple tangency. Partial results have already appeared in the literature, and we propose this work as an introduction to the use of the Chebotarev theorem in the context of incidence geometry. Finally, Veronese maps allow us to compute similar probabilities of intersection between a given curve and random curves of given degree.     

大数据背景下水厂自动投矾模型研究

根据某市自来水有限责任公司第二水厂的历史矾耗数据，建立矾耗流量关于原水浊度、温度等的动态矾耗模型. 通过对数据进行处理得到10900个合格且净水效果高效的数据，将筛选出的数据分为训练样本集和测试样本集. 在回归拟合中，通过拟合R2的大小将原水浊度划分为“低浊”“中浊”“高浊”3个区间，利用泰勒展开公式的非线性变量代换分别对3个区间建立不同的多项式回归模型，得到预测正确率约为72%，总的矾耗流量值约减少了9.6%的结果；在随机森林模型中，使用10900个合格数据，利用训练样本集，以“原水浊度”“pH值”“原水流量”和“水温”为输入变量，建立包含2000棵决策树的随机森林模型，得到预测正确率约为44. 21%，总的矾耗流量值增加了0.04%的结果. 从模型对合格数据的拟合优度看，随机森林模型比非线性回归模型效果更好；在平均绝对误差、平均绝对偏差百分比等评价指标上，前者均优于后者；但从历史数据检验的结果，模型的可解读性，模型的操作难度和推广角度看，分段二元非线性回归模型的优势更为突出.