Mellin 变换在处理光束漂移中的应用

从Mellin变换理论出发,推导了激光光束在湍流大气中斜程传输时的光束漂移公式,并在此基础上分析了准直激光光束漂移方差与靶标高度,光束半宽的关系.从结果可以看出,斜程传输在一定的距离内,靶标高度越高,光束的漂移方差越小;光束的初始半宽越大,光束的漂移方差越小.在斜程传输1km到10km距离下,随着靶标高度的逐渐增大,光束漂移方差的变化幅度越来越小,这时大气湍流的影响比水平传输时要小得多,上述理论结果与其他文献结果一致,从而也说明了Mellin变换理论在处理光束漂移方面的可行性.     

基于80C196MC单片机的电机软启动研究

本文重点介绍了Intel 800196MC的功能部件波形发生器（WFG）的工作原理,并结合新型晶闸管模块.详细说明了波形发生器在电机软起动控制中的应用。WFG的使用,简化了系统硬件设计和软件编程.使得波形控制简单可靠,增强了系统的抗干扰能力,取得了较好的电机软起动效果。     

Efficient parallel PML algorithms for truncating finite difference time domain simulations

In this paper, the parallel implementation of the stretched coordinate perfectly matched layer (SC-PML) and the wave equation PML (WE-PML) formulations is presented for truncating three-dimensional (3-D) finite difference time domain (FDTD) grids. In the proposed parallel algorithms, the FDTD computational domain is divided into contiguous non-overlapping subdomains using two-dimensional topology and the interprocessor communications between the neighboring subdomains are carried out by using the message passing interface (MPI) system. The performance of the proposed parallel algorithms has been studied by using a point source radiating in 3-D domains and performed on a network of PCs interconnected with Ethernet. It has been observed that the WE-PML parallel algorithm is approximately 2.3 faster than the SC-PML parallel algorithm.     

Peak load forecasting using Bayesian regularization,Resilient and adaptive backpropagation learning based artificial neural networks

Up to 7 days ahead electrical peak load forecasting has been done using feed forward neural network based on Steepest descent, Bayesian regularization, Resilient and adaptive backpropagation learning methods, by incorporating the effect of eleven weather parameters and past peak load information. To avoid trapping of network into a state of local minima, the optimization of user-defined parameters viz., learning rate and error goal has been performed. The sliding window concept has been incorporated for selection of training data set. It was then reduced as per relevant selection according to the day type and season for which the forecast is made. To reduce the dimensionality of input matrix, the Principal Component Analysis method of factor extraction or correlation analysis technique has been used and their performance has been compared. The resultant data set was used for training of three-layered neural network. In order to increase the learning speed, the weights and biases were initialized according to Nguyen and Widrow method. To avoid over fitting, early stopping of training was done at the minimum validation error.     

特高压交流输电线路中相绕击模拟试验研究

特高压交流输电线路ZBS2型酒杯塔的两地线间距大,因此研究其中相雷电屏蔽性能十分必要。文章采用按63﹕1的比例缩小的线路模型,考虑导线电压,使用更能逼近自然雷电的操作波进行了大量的冲击放电试验,得出了中相绕击的最大高度。根据文中的试验结果可知,换算出的中相临界绕击电流小于耐雷水平,验证了分别采用电气几何模型方法和先导模型方法得到的计算结果的正确性。试验结果还表明,ZBS2型杆塔线路中相有绕击的可能性,但不会导致闪络。     

Nanoenergetic Composites of CuO Nanorods,Nanowires, and Al‐Nanoparticles

This paper reports on the synthesis of the nanoenergetic composites containing CuO nanorods and nanowires, and Al‐nanoparticles. Nanorods and nanowires were synthesized using poly(ethylene glycol) templating method and combined with Al‐nanoparticles using ultrasonic mixing and self‐assembly methods. Poly(4‐vinylpyridine) was used for the self‐assembly of Al‐nanoparticles around the nanorods. At the optimized values of equivalence ratio, sonication time, and Al‐particle size, the combustion wave speed of 1650 m s⁻¹ was obtained for the nanorods‐based energetics. For the composite of nanowires and Al‐nanoparticles the speed was increased to 1900 m s⁻¹. The maximum combustion wave speed of 2400 m s⁻¹ was achieved for the self‐assembled composite, which is the highest known so far among the nanoenergetic materials. It is possible that in the self‐assembled composites, the interfacial contact between the oxidizer and fuel is higher and resistance to overall diffusional process is lower, thus enhancing the performance.     

[制造与维修工艺]高速铁路无砟轨道系统状态监测及预防性维修

高速铁路无砟轨道系统直接承载高速列车的高频冲击和振动,钢轨伸缩变形等状态变化都会严重影响列车安全,传统周期性检修易出现过修或失修问题,针对此,利用光纤光栅传感技术建立高铁无砟轨道系统状态监测平台,提出监测内容和监测点布置方案。通过对监测数据基本特征的分析,并结合轨道质量指数,建立了无砟轨道状态BP神经网络预测模型,预测了轨道服役状态。预测结果可指导铁路运营维护部门及时、合理地进行轨道养护维修,实现高铁轨道系统的预防性维修。     

Effect of hydrogen enrichment and electric field on lean CH4/air flame propagation at elevated pressure

Electric assisted combustion for hydrogen enriched hydrocarbons may even extend the lean burn limit and provide the further improvement on combustion stability. This study investigates the effect of hydrogen enrichment and DC electric field on lean CH₄/air flame propagation. Electric field inside the chamber was generated by mesh and needle electrodes. Effect of hydrogen enrichment on the ion mole fraction in the flame was discussed based on reaction mechanism included neutral and ion reactions. The flame propagation images, flame displacement speed were used to evaluate the combined influences of hydrogen enrichment and electric field on propagating flame. Results showed that the hydrogen addition would increase positive ions mole fraction and the peak value is mainly determined by H₃O⁺. This would be due to that CH increases with hydrogen fraction, which is the main species in the initial reaction for the ion reactions. Electric field effect about flame propagation was suppressed with hydrogen addition due to the competition between the increment in ion mole fraction and the decrement in flame time. Electric assisted combustion is more evident at leaner conditions and elevated pressure. The ratio of ionic wind velocity to flow velocity may be the determined factor to predict the electric field effect about propagating flame. The tendency based on this ratio is in accordance with the experimental results for various hydrogen fraction and equivalence ratio at elevated pressure.     

Effect of residual hydrogen content on the tensile properties and crack propagation behavior of a type 316 stainless steel

The tensile properties and crack propagation rate in a type 316 austenitic stainless steel prepared by vacuum induction melting method with different residual hydrogen contents (1.1–11.5 × 10⁻⁶) were systematically investigated in this research work. The room temperature tensile properties were measured under both regular tensile (12 mm/min) and slow tensile (0.01 mm/min) conditions, and the fracture properties of the tensile fractures with both rates were analyzed. It shows that the hydrogen induced plasticity loss of stainless steel strongly depends on the tensile rate. Under regular tensile condition, there is no plastic loss even when the hydrogen content is up to 11.5 × 10⁻⁶ while in the slow tensile condition, the plastic loss can be clearly identified rising with the increasing H contents. The fatigue crack propagation rate was tested at room temperature, and the crack growth rate formula (Paris) of the 316 stainless steels with varied H contents were obtained. The fatigue crack propagation rate test shows that the crack growth rate of the 316 stainless steel with 8.0–11.5 × 10⁻⁶ hydrogen is significantly higher than that of benchmark steel.     

锂离子电池模组热失控传播的结构因素影响分析

为优化锂离子电池模组的结构设计,通过热失控数值分析,结合COMSOL MULTIPHYSICS软件搭建了圆柱电池模组的三维热失控传播模型,研究不同排列结构和电池间隙下的热失控传播特性。结果表明：插排结构能有效降低热失控传播速率;增加模组中电池间隙,电池的热失控触发时间后移;在模组热失控后期,扩散速率加快。