Numerical study on flow control of ship airwake and rotor airload during helicopter shipboard landing

A numerical study on flow control of ship airwake during shipboard landing is carried out to address the effect of flow control devices on helicopter rotor airload. The in-house Reynolds Averaged Navier-Stokes (RANS) based solver Rotorcraft AeroDynamics and Aeroacoustics Solver (RADAS), with combination of momentum source approach is employed to conduct the helicopter shipboard landing simulation. The control effects of three aerodynamic modifications of ship superstructure, i.e. ramp, notch and flap, in different Wind-Over-Deck (WOD) conditions are discussed. From the steady simulation results, the effect of spatial variation of ship airwake on rotor airloads is concluded. The aerodynamic modifications reduce the strength of shedding vortex and increase rotor normal force through delaying and relieving flow separation, and therefore are beneficial to alleviate the limitation of control inputs. By contrast, the perturbation of unsteady ship airwake can cause the serious oscillation of rotor forces during shipboard landing. The unsteady simulations show that the turbulence intensity of ship airwake and oscillatory rotor airloading, represented by Root-Mean-Square (RMS) loading, can be remarkably reduced by the ramp and notch modifications, while the flap modification has adverse effect. It means that flow control devices have large potential benefits to alleviate the pilot’s workload and improve the shipboard landing safety, but they should be well designed to avoid the introduction of more vortex, which leads to increase in disturbance of flow field.     

基于有限元的平面变胞机构运动学研究

变胞机构具有在工作阶段切换时,杆件数目或运动数目及连接方式可变的特点,因此现有的基于有限元的机构运动学方法和分析软件无法直接用于变胞机构的分析.基于最小势能原理,推导出了任意曲线的滑动副单元和三节点焊接单元两种有限元模型.根据变胞机构的变胞特征,研究了基于有限元的运动学方法在变胞机构中的应用,给出了其计算步骤和流程.最后利用该方法对3种典型的平面变胞机构进行了分析,其结果表明该方法适合计算机的模块化编程和计算,对变胞机构的运动学研究有重要帮助.     

惯性器件结构设计与材料选用的规范化

概述惯性器件结构设计原则,分析材料选择及其工艺性、使用性、经济性与安全性的特点,从签署责任制方面阐述惯性器件设计文件会签中应注意的问题.     

王煜 著名CAE专家

目前,我在香港中文大学自动化与计算机辅助工程系任教.近期,主要从事CAE软件方面的研究,关且希望能在推动国产软年的发展方面做出一些有价值的成果.     

国内外航空乘务员招聘比较与探讨

从国内外航空公司乘务员的招聘过程中,比较各公司对乘务员要求和待遇上的差异,分析这些差异在实际工作中的表现和产生的效果。提醒国内航空公司更多的切实的关注乘务员的综合素质和真正的价值。     

防热材料热解与氧化性能试验技术研究

介绍了利用Arrhenius方程开展材料烧蚀热解性能动力学特性的基本原理，试验测试方法。并通过对炭酚醛材料烧蚀动力学参数的高频等离子体风洞试验研究，验证了采用时间历程积分在试验结果处理中的可靠性，在此基础上采用平板试验技术获得炭酚醛材料在600～1200K温度范围内的表面质量烧蚀率动力学方程，并将该方程所预测的结果与采用驻点烧蚀技术所获得的结果进行比较。结果显示：二者最大误差不超过5％，通过理论初步分析了二者之间存在差异的主要原因，并在试验比较分析的基础上，采用最大误差限理论分析了试验结果的可靠性。     

一种嵌入式仓库智能监控报警终端设计

针对中小型企业仓库管理智能化发展需要,结合现代计算机图像处理、模式识别等相关技术,设计一种移动图像智能监控报警终端。终端采用三星公司最新推出的基于ARM11架构的S3C6410芯片作为处理器,还应用Linux2.6.36版本内核和initramfs起根文件系统。文中给出终端硬件组成、整体结构及软件设计。终端测试结果达到预期,可以实时监测摄像头范围之内的场景,当监控图像发生变化时立即报警。     

结合颅骨形态特征与神经网络的民族判别

针对颅骨民族判别问题，提出结合颅骨形态特征与神经网络的判别方法，可以推进法医人类学的发展，加快探索民族发展历程。首先，根据颅骨形态学相关研究，提取36个维吾尔族和汉族颅骨数据的几何特征；其次，采用反向传播神经网络（BPNN）对特征向量进行民族判别，并通过Adam算法对网络进行优化，避免陷入局部最优值，添加正则化项保证算法稳定性；最后，分别采用2种网络结构进行对比实验，输入层、隐藏层和输出层的神经元个数分别为36、6、2和36、12、2，并设置不同初始学习率进行对比实验。结果表明:隐藏层神经元个数为12、学习率为0.000 1时，分类精度最高，测试阶段平均准确率最高为97.5%。为了验证所提方法的普适性，生成116例国外颅骨数据进行实验，测试阶段平均准确率为90.96%。相比较于支持向量机（SVM）、决策树、KNN、Fisher等机器学习方法，所提方法学习能力更强且分类精度有明显提升。      

TS-InSAR analysis for monitoring ground deformation in Lanzhou New District,the loess Plateau of China,from 2017 to 2019

Large-scale land creation projects involving the cutting of mountains to infill gullies for construction have been carried out in Lanzhou New District (LZND). However, there is an urgent need for comprehensive and detailed research on the spatiotemporal evolution of ground deformation in LZND. Based on Sentinel-1A SAR data, combined with the urban geological background, the ground deformation in LZND from 2017 to 2019 was analysed. Two independent, multi-temporal techniques, persistent scatterers interferometry (PS-InSAR) and the small baseline subset (SBAS-InSAR), were used to calculate the deformation time series, and the results were cross-verified. The time series-monitoring results of the SBAS and PS calculations exhibited strong consistency in LZND and verified the high reliability of the experimental results. The results showed the whole surface of the LZND from March 2017 to October 2019 maintained stability, and the deformation rate was primarily in the range of ?10 to 10 mm/year. However, ground deformation in the Xicha area was evident. The maximum annual deformation rates monitored by SBAS-InSAR and PS-InSAR were ?52.48 mm/year and ?56.35 mm/year, respectively. The most typical deformation areas include the built-up area and the land creation area. The surface subsidence area was concentrated in the filling area. The ground deformation range of LZND kept expanding and accelerating from 2017 to 2019. Land creation, urban construction, geology and precipitation were the primary factors contributing to local severe ground deformation. The results of this study provide reference for the regional urban planning in LZND.