Effects of welding parameters and welding sequence on residual stress and distortion in Al6061-T6 aluminum alloy for T-shaped welded joint

The distribution of temperature and then the distribution of residual stress and distortion in the stiffened aluminum alloy Al6061-T6 plates under the metal inert gas (MIG) welding process were investigated by three dimensional thermo-mechanical coupled finite element model using Ansys software. The properties of materials were considered temperature-dependent and the filler metal was added to the workpiece by the element birth and death technique. In three modes of current, two different speeds and two various sequences, the distribution of residual stress and distortion were calculated and analyzed. The results showed that increase in welding speed decreased the vertical deflection in the plate, transverse shrinkage and angular distortion of plate and the lateral deflection of stiffener, but increased the maximum longitudinal tensile stress in the plate and stiffener. Furthermore, increase in current increased the residual stress and deformation in the plate and stiffener, and the change in the welding sequence changed the distribution of the distortion in the plate and the stiffener without significant change in the distribution of the longitudinal residual stress.     

部分传输序列的遗传模拟退火搜索方法

在正交频分复用(OFDM)系统中,基于遗传算法的部分传输序列(GA-PTS)技术有效地降低了 PTS 的计算复杂度,但在 改进峰值-平均功率比(PAPR)性能方面却并不理想。 为此,提出在遗传算法中嵌入模拟退火(SA)算子从而构造一种混合的遗 传模拟退火(GSA)算法,并把它应用于对 PTS 的最优相位因子进行搜索。 首先,通过对 PTS 相位因子编码形成染色体,采用随 机元素组成的染色体作为遗传算法的初始群体,并评估每个染色体的适应度值。 然后,根据适应度值选择染色体,建立染色体 的变异规则和交叉规则,对群体进行迭代进化。 最后,群体中的染色体利用退火温度进行更新,从而产生出新的下一代种群。 仿真结果说明,与 GA-PTS 方案相比,该方法不仅能降低计算负担,而且能够有效地降低 OFDM 系统 PAPR 值。     

Enhanced control strategies for a hybrid battery/photovoltaic system using FGS-PID in grid-connected mode

This paper suggests improved control strategies using Fuzzy Gain Scheduling of Proportional-Integral-Derivative (FGS-PID) controller for a hybrid Photovoltaic (PV) and Battery Energy Storage (BES) system under different weather conditions. The proposed scheme is implemented using a two-level control system structure, combining the benefits of the PID as well as the fuzzy logic controller (FLC) for maximum power point tracking (MPPT). Ziegler-Nichols tuning method is also employed to select the initial values of PID gains. Within the period of steady-states and transients, FGS-PID adopts the gains to ensure the stability of the control scheme. It also damps out transient fluctuations and reduces settling time. Also, BES could be employed to provide a stable and reliable power from the output of PV sources to loads. It can enhance the performance of the entire power system during the grid-connected mode. The simulation results under Matlab/Simulink show that the suggested control strategies are robustness, fast transient response and proper steady-state performance in the grid-connected mode in comparison other presented methods.     

基于时空的弱点状运动目标检测技术

如何在复杂背景下持续有效地检测目标位置,一直是研究者们需要面对的主要挑战。本文在研究红外点状移动目标特征的基础上,根据目标无纹理,无形状的特性,提出一种改进的形态学目标增强算法,并利用目标连续时空不变性检测目标。首先,建立多尺度的图像金字塔,在每层上采用改进的形态学算法快速、粗糙定位小目标。然后进一步的根据目标在时空上的位置相关性,提出基于目标运动特征分析的精确检测方法。得到精确稳定的检测结果。最后实验结果表明与经典的形态学检测算法及其他算法相比,该技术能更有效地检测弱小目标,具有更高的鲁棒性。     

基于压缩感知的高阶MIMO系统信道估值算法

针对通信网络中的天线数量巨大，很难完成对信道的有效计算与估值。借助于高阶多输入多输出（MIMO）系统的可靠性，提出了一种基于压缩感知的信道估值高阶MIMO系统。设计了一种简单的导频结构，以降低计算复杂度；利用导频序列长度可以随着信道稀疏度变化情况自适应的调整，从而节省了导频资源的开销。仿真实验表明，与传统的信道估计算法比较，在相同的信道估计精度条件下，HMCE-CS算法可以降低平均导频序列长度；或者在相同的导频序列长度条件下，HMCE-CS算法可以提高信道估计精度，验证了该算法的有效性。     

基于双面组件的可调支架光伏发电系统仿真研究

以双面光伏组件和可调支架系统为基础,以青海格尔木为模拟地点,利用PVsyst光伏仿真软件,分析了不同调节次数的可调支架系统与固定支架系统在组件正面和背面辐射量、系统发电量、系统收益的差异。研究结果表明：通过调节支架改变光伏组件的角度后,组件最低点离地高度也在变化,直接影响组件正面和背面的辐射接收;光伏方阵前后间距影响土地利用率（GCR）,土地利用率降低后,背面的辐射量和系统发电量都有一定的增加;相对于固定支架双面发电系统,可调支架双面系统在不同调节次数下的组件背面全年辐射量均有一定降低,但整体的发电量得益于正面辐射的增益,最高可达4.8%左右;技术和经济比较结果显示,双面组件采用可调支架系统,每年2次的调节方式,25年生命周期内系统收益最高。文章还分析了单面发电组件和双面组件系统使用可调支架的经济性对比,在相同的调节次数下,双面组件系统的增益明显高于单面组件系统。本文的研究成果对可调支架双面组件发电系统的设计具指导作用。     

槽波透射勘探技术在寺河矿的精准应用

在井下综采工作面一侧巷道内激发槽波,另一侧巷道中接收通过采面透射的槽波。利用煤层与岩层的物理力学差异,分析在煤层中激发和接收到的槽波,以此来探查综采工作面中地质构造、煤体破碎区、应力集中区的位置,从而为后期探测地质构造参数、煤体破碎区注浆、应力集中区消突等工作的顺利进行提供基础数据,提高后期工程实施的针对性。     

SiO2颗粒增强酚醛树脂基摩擦材料力学性能研究

为探讨陶瓷颗粒对树脂基摩擦材料力学性能的影响,以SiO_2颗粒增强酚醛树脂基摩擦材料为例,利用三点弯曲实验研究颗粒特征对弯曲强度的影响,建立材料内部弹性应力场分布模型,并从细观力学角度进行分析。实验结果表明:添加二氧化硅陶瓷颗粒后,复合材料的弯曲强度降低、弹性模量升高;复合材料弯曲断裂截面显示脆性断裂特征,断裂过程中裂纹遇到颗粒贯穿通过;复合材料弯曲强度随颗粒含量增加而降低,随颗粒弹性模量增加先减小后增大。理论分析表明:陶瓷复合树脂基摩擦材料内部最大应力值位于颗粒边缘处;最大应力值随颗粒与基体弹性模量比值增大而增大;复合材料的平均应力与颗粒的含量成正相关。实验和理论研究表明,陶瓷颗粒添加引起材料内部应力集中,且与颗粒弹性模量和颗粒含量成正相关。     

Estimating underground mine ventilation friction factors from low density 3D data acquired by a moving LiDAR

Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limited to the quantity of air moving through any given heading. Because computer-aided modelling, simulation, and ventilation system design tools have improved, it is now important to ensure that developed models have the most accurate information possible. This paper presents a new technique for estimating underground drift friction factors that works by processing 3 D point cloud data obtained by using a mobile Li DAR. Presented are field results that compare the proposed approach with previously published algorithms, as well as with manually acquired measurements.     

冷连轧机带钢切边宽度自动设定研究

宽展是冷连轧机切边剪切边宽度设定的重要考虑因素。影响宽展的因素较多,若考虑各影响因素,建立宽展模型十分困难。为此,在满足生产需求的前提下,通过大量数据分析,拟合出宽展系数计算多项式,进而可计算出满足需求的考虑宽展的切边剪宽度设定值,并通过自动化系统的改造实现了切边剪宽度的自动设定。