Oxygen vacancy in magnesium/cerium composite from ball milling for hydrogen storage improvement

The hydrogen sorption performance of Mg is constrained by the difficulties of hydrogen dissociation on particle surface and mass transfer in particle bulk. This work focuses on oxygen vacancy and its effect on the performance of Mg-xCeO₂ (x = 0.7, 1.5, 3, and 6 mol.%) from ball milling for hydrogen storage. The HRTEM observation shows that the crystal domains of Mg from ball milling are reduced to nanoscale by the addition of hard CeO₂ nanoparticles. The XRD and XPS characterization shows that during heating for hydrogenation, some O atoms in CeO₂ transfer to Mg and form MgO, and CeO₂ converts to Ce₆O₁₁ with oxygen vacancies. The isothermal absorption (p-c-T) analysis shows that the hydrogen capacity of the materials increases with the increase of CeO₂ additive, and the optimum addition is 3.0 mol.%. The DSC analysis shows that with the addition of 3.0 mol.% of CeO₂, the hydrogen desorption peak temperature is 35 °C lower than that of pure MgH₂, and the calculated activation energy deceases by 31.3 kJ/mol. The improvement of hydrogen sorption performance is mainly attributed to the formation of oxygen vacancies.     

Nanowires embedded porous TiO2@C nanocomposite anodes for enhanced stable lithium and sodium ion battery performance

A porous carbon nanocomposite with embedded TiO₂ nanowires (NWs) was synthesized using a two-step synthetic method in which carbon matrix was obtained by carbonizing a vacuum dried gel. This unique structure in which TiO₂ nanowires uniformly distributed in and tightly bonded to the carbon matrix shortened the electron transport path and reduced the transmission resistance. Nanoporous structure ensured continuous transfer of Li⁺/Na⁺ and supplied a large specific surface area of 280.82 m² g⁻¹ to provide more active sites. Different from other existing works on TiO₂@C anode materials with TiO₂ loading higher than 60 wt%, the obtained very small amount of TiO₂ (~12 wt%) improved the electrochemical and long-cycle performance of carbon substrate with TiO₂ NWs embedded significantly, due to uniformly distributed TiO₂ NWs throughout the carbon matrix. These TiO₂@C composite anodes could deliver a specific capacity of 286 mA h g⁻¹ at 0.3 C, 197 mA h g⁻¹ at 0.15 C for lithium and sodium ion batteries, respectively. It maintained remarkably stable reversible capacities of 128 and 125 mA h g⁻¹ for lithium and sodium ion batteries at 3 C during 2500 cycles, respectively. Smaller fluctuations and smoother curves demonstrated that sodium ion storage was more stable than lithium ion storage for the TiO₂@C composite anode. In addition, the capacitive contributions of TiO₂@C in both systems are quantified by kinetics analysis.     

Analysis of electrochemical impedance of polyaniline films prepared by galvanostatic,potentiostatic and potentiodynamic methods

Polyaniline (PANI) films have been deposited on stainless steel (SS) substrate by galvanostatic, potentiostatic and potentiodynamic methods. Electrochemical impedance spectra of the electrodes have been analyzed using a transmission line model consisting of two rails of finite resistances. The impedance spectra of the galvanostatically prepared electrodes are similar in shape to those of potentiostatically grown electrodes. The resistance of aqueous pore (R_aq) due to ionic doping–dedoping process is greater than the resistance (R_p) of electronic charge-transfer on polymer chain. These parameters exhibit an increase in magnitude with thickness of PANI, as expected from the transmission line theory. The shape of impedance spectra of potentiodynamically grown PANI, however, is different and its R_aq ≤ R_p. The impedance parameters of potentiodynamically prepared PANI/SS electrodes have been found to depend on the sweep rate used for the deposition of PANI. Several possible explanations have been discussed to understand the influence of sweep rate during deposition on impedance parameters of the electrodes. In contrast to the behavior of PANI deposited by galvanostatic and potentiostatic methods, R_p decreases with an increase in thickness of PANI deposited by the potentiodynamic method. The effect of concentration of aniline used for the deposition of PANI on impedance parameters has also been studied. The results of capacitance of PANI obtained from the ac impedance studies have been found to be comparable with those obtained from the cyclic voltammetric studies.     

不同孔型平板气膜冷却特性的数值模拟

为研究不同射流孔型对气膜冷却效率的影响,基于SIMPLEC算法,采用RNGκ-ε湍流模型,对射流倾斜角为35°的圆柱孔、扩散孔和横向扩散孔的平板气膜冷却模型进行了数值模拟。得到了不同吹风比M下的3种孔型的绝热气膜冷却效率曲线、速度矢量图和壁面温度分布。结果表明：横向扩散孔的气膜冷却效果优于圆柱孔和扩散孔,其产生的反向涡旋对的尺度最小,孔间的气膜冷却效果也较好。     

用解析法分析立辊轧机冲击振动信号

为降低复杂信号模型识别困难,采用把线性参数和非线性参数分开识别的方法．该法可用于对立辊轧机冲击振动加速度信号的识别．通过识别到的加速度信号解析式,可得到振动速度及振动位移．该解析法具有较高的消噪能力,并可识别出高精度的轧机系统振动模态参数．     

Correlation analysis based MIMO neuro-fuzzy Hammerstein model with noises

A novel identification algorithm for neuro-fuzzy based MIMO Hammerstein system with noises by using the correlation analysis method is presented in this paper. A special test signal that contains independent separable signals and uniformly random multi-step signal is adopted to identify the MIMO Hammerstein system, resulting in the identification problem of the linear model separated from that of nonlinear part. As a result, it can circumvent the problem of initialization and convergence of the model parameters encountered by the existing iterative algorithms used for identification of MIMO Hammerstein model. Moreover, least square method based parameter identification algorithms of dynamic linear part and static nonlinear part are proposed to avoid the influence of noise. Examples are used to illustrate the effectiveness of the proposed method.     

A two-level parser for patent claim parsing

Patent claim parsing can contribute in many patent-related applications, such as patent search, information extraction, machine translation and summarization. However, patent claim parsing is difficult due to the special structure of patent claims. To overcome this difficulty, the challenges facing the patent claim parsing were first investigated and the peculiarities of claim syntax that obstruct dependency parsing were highlighted. To handle these peculiarities, this study proposes a new two-level parser, in which a conventional parser is imbedded. A patent claim is pre-processed in order to remove peculiarities before passed to the conventional parser. The process is based on a new dependency-based syntax called Independent Claim Segment Dependency Syntax (ICSDS). This two-lever parser has demonstrated promising improvement for patent claim parsing on both effectiveness and efficiency over the conventional parser.     

A novel approach to CNC machining center processing parameters optimization considering energy-saving and low-cost

NC machining is currently a machining method widely used in mechanical manufacturing systems. Reasonable selection of process parameters can significantly reduce the processing cost and energy consumption. In order to realize the energy-saving and low-cost of CNC machining, the cutting parameters are optimized from the aspects of energy-saving and low-cost, and a process parameter optimization method of CNC machining center that takes into account both energy-saving and low -cost is proposed. The energy flow characteristics of the machining center processing system are analyzed, considering the actual constraints of machine tool performance and tool life in the machining process, a multi-objective optimization model with milling speed, feed per tooth and spindle speed as optimization variables is established, and a weight coefficient is introduced to facilitate the solution to convert it into a single objective optimization model. In order to ensure the accuracy of the model solution, a combinatorial optimization algorithm based on particle swarm optimization and NSGA-II is proposed to solve the model. Finally, take plane milling as an example to verify the feasibility of this method. The experimental results show that the multi-objective optimization model is feasible and effective, and it can effectively help operators to balance the energy consumption and processing cost at the same time, so as to achieve the goal of energy conservation and low-cost. In addition, the combinatorial optimization algorithm is compared with the NSGA-II, the results show that the combinatorial optimization algorithm has better performance in solving speed and optimization accuracy.     

U71Mn钢重轨轨头淬火应力场的计算机模拟

采用有限元法研究了重轨轨头在淬火过程中的应力场分布。在模拟计算过程中利用等效热容法处理相变潜热对温度场的影响,利用等效线膨胀系数法处理相变引起的组织应力,并考虑了材料非线性参数对温度场的影响。结果表明,温度模拟结果与实测结果相吻合,同时喷风淬火能产生较小的残余热应力,从而避免了钢轨的变形和开裂。     

双喷嘴挡板电液伺服阀主要参数的优化

以国产双喷嘴挡板电液伺服阀为研究对象,推导出其数学模型。根据电液伺服阀的实际结构参数,运用Simulink仿真软件对数学模型进行仿真,得到电液伺服阀闭环阶跃的响应图和伯德图。通过改变目标参数Kvf、ωmf、ξ′mf的大小,得到不同的电液伺服阀伯德图;通过分析电液伺服阀动态性能的变化,从而达到其参数优化的目的。