一种子阵级DAR同时多波束拟合测角方法

针对数字同时多波束技术在子阵级数字阵列雷达中的应用问题,提出了一种适用于子阵级数字阵列雷达的同时多波束测角方法。首先介绍了如何通过数字加权的方式形成同时接收多波束,然后基于比幅法建立了同时多波束拟合测角模型,给出了同时多波束拟合测角方法的实现流程和具体步骤,最后进行仿真验证及分析。仿真结果表明:该方法具有与数字和差单脉冲相当的测角精度,且在保持一定测角精度的情况下,同时多波束拟合测角方法可以获得更宽的测角范围,具有良好的工程化应用价值。

基于指根边缘夹角平分线拟合的掌纹定位方法

针对移动终端复杂背景引起的感兴趣区域(Region of interest,ROI)定位不准确性,提出一种基于指间边缘夹角角平分线的掌纹ROI定位方法.首先在YCbCr颜色空间提取边缘,即追踪掌纹轮廓,然后用椭圆模型去除伪边缘和噪声,通过形态学操作对实际边缘进行平滑和修补,从而将指根边缘区域化.在所得两个边缘区域上,用最小二乘法拟合边缘夹角平分线来定位指窝点.该方法能有效去除指根附近背景的干扰,克服手掌轻微旋转引起的ROI定位偏差,实验表明该方法在移动设备环境下能够达到较高的正确率和认证精度.

基于机器学习敏感性分析的RC板柱节点冲切角预测模型

为准确预测板柱节点冲切破坏倾角,本文收集了67组破坏倾角数据,建立基于机器学习的随机森林预测模型,并调整超参数使模型更加精确。通过RMSE(root mean square error)、MAE(mean absolute error)、R23个指标对预测结果进行检测,结果表明随机森林模型,在训练集和测试集上预测精度都较高。通过SHAP(Shapley Additive exPlanation)可解释方法,对随机森林预测模型的影响因素进行敏感性分析,发现混凝土抗压强度、钢筋屈服强度和钢筋配筋率对倾角的影响最大。选取上述3个影响因素进行拟合,得到RC板柱节点的冲切角计算公式,计算结果与实际值吻合良好。本文结果可为板柱结构性能研究提供参考。

涡旋压缩机型线加工方法分析(上)

分析圆的渐开线的几种常用加工方法、加工特性和一些控制误差 ,提出X Y轴控制的直线逼近加工方法 ,及适用于型线的范围和对精度要求。提出X C轴控制的展成法和消除曲线拟合及部分数控误差的方法。同时分析型线中心修正部分传统所用的X Y轴控制加工误差 ,提出用X Y C轴控制的加工方法 ,改善刀具磨损及热变形因素造成的加工误差。

一种基于视觉的瓷砖尺寸在线检测系统

介绍了一种基于线阵CCD的瓷砖尺寸在线视觉检测系统,对系统进行了设计,并提出了系统的标定方法。采用了一种改进的基于灰度矩的亚像素边缘定位算法对边缘进行了精确定位,随后根据边缘点数据拟合出瓷砖的角点,最终根据角点的相对位置求出瓷砖的各个尺寸参数。实验结果表明,该系统具有实时、非接触、速度快、精度高以及现场抗干扰能力强等优点,可以满足一般瓷砖在线尺寸检测的需要。

Seismic dip estimation based on the twodimensional Hilbert transform and its application in random noise attenuation

In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.

Numerical and physical simulation of new SPD method combining extrusion and equal channel angular pressing for AZ31 magnesium alloy

A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.The components of ES forming die were manufactured and installed to Gleeble1500D thermo-mechanical simulator.The microstructure observations were carried out on the as-extruded rods(as-received) and ES formed rods.From the simulation results,ES forming can increase the cumulative strain enormously and the volume fraction of dynamic recrystallization.From the physical modeling results,the microstructures can be refined.

Helium-3 global optical model potential with energies below 250 MeV

A new set of global phenomenological optical model potential parameters has been obtained for helium-3 projectile, by simultaneously fitting the experimental data of helium-3 total reaction cross sections and elastic scattering angular distributions in the mass range of target nuclei 20〈〈A〈209 at incident energies below 250 MeV. A comparison has been made between the extracted helium-3 global optical model potential parameters and the existing ones. The calculated results of total reaction cross sections and elastic scattering angular distributions are also agreement. compared with experimental data with their satisfactory