Ab initio calculations on the mechanism of isobutane and 2-butene alkylation reaction catalyzed by hydrofluoric acid

Ab initio method was employed to determine the mechanism of alkylation reaction of 2-butene with isobutane. The results indicated that 2-butene is rapidly protonated to form sec-butyl carbonium ion, which then reacts with isobutane to form tert-butyl carbonium ion. The resulting carbonium ion is then deprotonated to form isobutene that reacts rapidly with tert-butyl carbonium ion to form trimethylpentane (TMP) carbonium ion. Finally, the TMP⁺ carbonium ion is converted to TMP via the hydride transfer process. The transition states of the interactions were obtained by using the SCAN method (a calculation key word for potential energy surface) first and then the intrinsic reaction coordinates were traced using the Gaussian program. In addition, the energy changes and geometric parameters of the interactions were analyzed. The computed results indicated that the energy barriers are close to or less than zero for the interaction of isobutane with protonated 2-butene or for the interaction of tert-butyl carbonium ion with isobutene, suggesting rapid reaction steps of the carbonium ions. The 2,2,3-TMP is kinetically controlled, while the formation of 2,2,4-TMP is controlled by reaction equilibrium. The calculated results were in good agreement with the experimental results.     

Unsupervised Scale-Consistent Depth Learning from Video

International Journal of Computer Vision - We propose a monocular depth estimation method SC-Depth, which requires only unlabelled videos for training and enables the scale-consistent...     

From text to graph: a general transition-based AMR parsing using neural network

Neural Computing and Applications - Semantic understanding is an essential research issue for many applications, such as social network analysis, collective intelligence and content computing,...     

一种PC式数字录像机软件系统的设计与实现

介绍了一种PC(个人计算机)式数字录像机软件系统的设计与实现,给出了该软件系统的组成框架,对系统主要功能的设计与实现进行了简介,包括图像预览、录像与回放、移动侦测与遮挡、电子地图等。文章给出了系统设计中的多厂家设备支持、系统性能优化两个关键问题的设计与实现。该PC式数字录像机软件系统界面友好、功能完善、运行稳定,用户易于掌握使用,同时具有良好的可扩展性,在实际使用中效果良好。     

Measurement of density of the gap states ina-Si:H by the normalization of photoconductivity

The spectra of the optical absorption coefficient in low absorption region are obtained by using a normalization procedure for the photoconductivity spectra. The results are explained in terms of the optical transition of electrons from localized states in the exponential valence band tail and in dangling bond states 1.0 eV below the conduction band edge to extended conduction band states. Then the density of the gap states below the Fermi levelE _F is obtained. From the investigation of recombination kinetics, the average density of the gap states over the range of ) and the density of the gap states above the Fermi levelE _F are obtained. These indicate that the width of the conduction band tail is smaller than that of the valence band tail.     

Large tree classifier with heuristic search and global training

In the tree classifier with top-down search, a global decision is made via a series of local decisions. Although this approach gains in classification efficiency, it also gives rise to error accumulation which can be very harmful when the number of classes is very large. To overcome this difficulty, a new tree classifier with the following characteristics is proposed: 1) fuzzy logic search is used to find all ``possible correct classes,' and some similarity measures are used to determine the ``most probable class'; 2) global training is applied to generate extended terminals in order to enhance the recognition rate; 3) both the training and search algorithms have been given a lot of flexibility, to provide tradeoffs between error and rejection rates, and between the recognition rate and speed. A computer simulation of the decision trees for the recognition of 3200 Chinese character categories yielded a very high recognition rate of 99.93 percent and a very high speed of 861 samples/s, when the program was written in a high level language and run on a large multiuser time-sharing computer.     

Application of electrode materials and catalysts in electrocatalytic treatment of dye wastewater

The dye industry produces a large amount of hazardous wastewater every day worldwide, which brings potential threaten to the global environment. As an excellent method for removal of water chroma and chemical oxygen demand, electrocatalytic methods are currently widely used in the treatment of dye wastewater. The selection and preparation of electrode materials and electrocatalysts play an important role on the electrocatalytic treatment. The aim of this paper is to introduce the most excellent high-efficiency electrode materials and electrocatalysts in the field of dye wastewater treatment. Many electrode materials such as metal electrode materials, boron-doped diamond anode materials and three-dimensional electrode are introduced in detail. Besides, the mechanism of electrocatalytic oxidation is summarized. The composite treatment of active electrode and electrocatalyst are extensively examined. Finally, the progress of photo-assisted electrocatalytic methods of dye wastewater and the catalysts are described.     

铜锌铝合金表面非线性振荡花样的研究

在Ｃｕ－Ｚｎ－Ａｌ形状记忆合金表面观察到尚未被人们认识的非线性振荡花样。这些花样经计算机图像处理得知，在空间和时间上明显呈现分形特征。这种振荡花样的产生可能与未知相变的预转变过程有关。     

Nonlinear tracking control of underactuated cranes with load transferring and lowering: Theory and experimentation

A bridge crane is a complicated nonlinear underactuated mechatronic system, for which high-speed positioning and anti-swing control is the kernel objective. Existing methods for varying cable length cranes require either linearizations or approximations, when performing analysis, and they usually assume small load swing; moreover, the ranges of the tracking errors cannot be guaranteed during the overall process. Motivated by these facts, we present a new tracking scheme for cranes with load horizontal transportation and lowering control, which achieves simultaneous load swing suppression and elimination. To the best of our knowledge, the proposed method yields the first feedback closed-loop control result not needing linearization or approximation operations to the original nonlinear crane dynamics with cable length variation, while relaxing the common assumption imposed on load swing associated with existing methods. It can also guarantee that the tracking errors are always within a priori set bounds and converge to zero rapidly. Lyapunov-like analysis is implemented to support the theoretical derivations. We carry out hardware experiments to illustrate the superior control performance of the new method.