Improved synthesis of dihydrothiophenes derivatives under ultrasound irradiation

A series of dihydrothiphenes derivatives were synthesized via the four‐component reaction of aldehyde, malononitrile, 1,3‐thiazolidinedione, and piperidine at room temperature under ultrasound irradiation. Compared with the conventional methods, the remarkable advantages of this method are operational simplicity, higher yield, and shorter reaction time. J. Heterocyclic Chem., (2011).     

A green method for the synthesis of thiochromene derivatives in ionic liquids

Controlling the pH value by changing the negative ion of ionic liquids, the same reactions of aromatic aldehyde, 2‐(2,3‐dihydrothiochromen‐4‐ylidene) malononitrile and malononitrile product unaromatized and aromatized 6H‐benzo[c]thiochromene derivatives in high yields. The nice features of these procedures include mild reactions condition, simple operations, high yields, and environmentally benign. J. Heterocyclic Chem., (2011).     

An efficient synthesis of pyrazolo[3,4‐b]quinolin‐5(6H)‐one derivatives in ionic liquid

A series of 4‐aryl‐3,7,7‐trimethyl‐1‐phenyl‐7,8‐dihydro‐1H‐pyrazolo[3,4‐b]quinolin‐5(6H)‐ones were synthesized via the three‐component reaction of aromatic aldehydes, 5,5‐dimethyl‐1,3‐cyclohexandione and 5‐amino‐3‐methyl‐1‐phenylpyrazole in ionic liquid without using any catalyst. This protocol has the advantages of easier work‐up, milder reaction conditions, short reaction time, and environmentally benign procedure. J. Heterocyclic Chem., (2011).     

MULTIPLE SOLUTIONS TO A SECOND-ORDER m-POINT BOUNDARY VALUE PROBLEM

In this paper, we are concerned a class of second-order m-point boundary value problem. The existence results of at least three positive solutions are given by using a fixed-point theorem and imposing growth conditions on the nonlinear term, which depends on the first derivative.     

改进的卷积神经网络源代码相似性度量方法

源代码相似性是指不同代码段功能上的相似程度,是软件工程领域一项重要的研究问题.现有的方法主要从文本、结构两方面,利用代码的统计学特征计算相似性,其最大缺点就是无法表达代码的语义特征.为解决此类问题,提出了一种融合统计信息的卷积神经网络（statistics information for code embedding convolutional neural networks, SICE-CNN）源代码相似性检测方法.该方法首先通过词嵌入对源代码进行信息表示,获取代码的词嵌入向量信息;其次,构建CNN训练模型学习源代码文档的嵌入表示;最后,计算源代码对的余弦相似值.实验表明,该方法和一般词嵌入方法相比提高了一定的性能,能较好地检测源代码的语义相似性.     

Moving mesh finite difference solution of non-equilibrium radiation diffusion equations

Numerical Algorithms - A moving mesh finite difference method based on the moving mesh partial differential equation is proposed for the numerical solution of the 2T model for multi-material,...     

Lanczos method for large-scale quaternion singular value decomposition

In many color image processing and recognition applications, one of the most important targets is to compute the optimal low-rank approximations to color images, which can be reconstructed with a small number of dominant singular value decomposition (SVD) triplets of quaternion matrices. All existing methods are designed to compute all SVD triplets of quaternion matrices at first and then to select the necessary dominant ones for reconstruction. This way costs quite a lot of operational flops and CPU times to compute many superfluous SVD triplets. In this paper, we propose a Lanczos-based method of computing partial (several dominant) SVD triplets of the large-scale quaternion matrices. The partial bidiagonalization of large-scale quaternion matrices is derived by using the Lanczos iteration, and the reorthogonalization and thick-restart techniques are also utilized in the implementation. An algorithm is presented to compute the partial quaternion singular value decomposition. Numerical examples, including principal component analysis, color face recognition, video compression and color image completion, illustrate that the performance of the developed Lanczos-based method for low-rank quaternion approximation is better than that of the state-of-the-art methods.

     

Global regularity of the 2D magnetohydrodynamic equations with fractional anisotropic dissipation

This paper is dedicated to establishing the global regularity for the two dimensional magnetohydrodynamic equations with fractional anisotropic dissipation when the fractional powers are restricted to some certain ranges. In addition, the global regularity results for the two dimensional magnetohydrodynamic equations with partial dissipation are also obtained. Consequently, these results bring us more closer to the resolution of the global regularity problem on the two dimensional magnetohydrodynamic equations with standard Laplacian magnetic diffusion.     

创新流体实验仪器,探索创新型人才培养

实验教学是理论联系实践的关键环节,对于学生的综合素质培养和提高有重要意义,而传统的实验教学模式已难以满足社会对工程应用型创新人才的要求。本文结合流体力学实验教学改革实践,探讨了改进自制流体力学实验仪器设备对提升大学生创新精神和创新能力的作用。创新化的实验教学,有助于激发学生自主实验的积极性,进而增强了他们应用已学知识解决复杂实际问题的创新能力。     

矿井提升钢丝绳改性氧化石墨烯润滑油减摩特性研究

针对恶劣提升工况下润滑失效导致的提升钢丝绳内部钢丝摩擦磨损严重的问题,开展改性氧化石墨烯润滑油减摩特性研究. 首先,制备十八胺官能化氧化石墨烯(ODA-GO)及其水合肼还原材料(ODA-rGO),分析其化学结构、表面形貌、片层间距和缺陷,探究其在钢丝绳润滑油IRIS中的分散性;接着,用四球机评价改性润滑油的减摩抗磨性能并研究其润滑机理;最后,评判ODA-GO改性油对钢丝减摩的改进效果. 结果表明:ODA通过酰胺化反应和亲核取代反应接枝在GO表面,ODA-GO拥有高接枝密度的十八烷基链,并在IRIS中分散性较好,ODA-rGO则相反,但在最优添加量下ODA-rGO的抗磨减摩性优于ODA-GO;改性石墨烯基材料会附着在摩擦接触表面,并填补已损伤区域,从而减少磨损;ODA-GO改性油使钢丝间摩擦系数降低10%,疲劳磨损显著降低.