摘要：作物茎秆膨胀和收缩变化与其水分状态密切相关,实时监测茎秆的膨胀和收缩变化能够及时掌握作物水分状态,对指导灌溉、提高农业水资源利用率具有重要意义。目前,对于作物茎秆膨胀和收缩变化的监测主要采用基于线性微位移测量原理的传感器,通过测量茎秆的膨胀和收缩引起的位移变化来反映水分状态,存在体积大、价格高、安装不便等问题。为此,该研究提出了一种基于压阻效应的柔性可穿戴传感器,采用柔性压力电极作为传感元件,贴附在作物茎秆表面,通过监测茎秆膨胀和收缩引起的压力变化来反映作物的水分状态,压力检测电路和数据采集电路将作物茎秆的压力信号转换成电信号进行输出和存储。首先在实验室环境下对传感器性能进行测试和标定,然后在温室环境下将传感器安装在番茄茎秆上观测番茄茎秆的压力变化,并与线性微位移传感器观测结果进行比较,最后在充分灌溉和水分亏缺2种条件下观测番茄茎秆的膨胀和收缩变化。结果表明,柔性压力传感器稳定性测试的平均相对变化率为0.109%;弯折前后引起的输出变化非常小,可以忽略不计;标定结果的决定系数大于0.99,最合适的工作压力范围为2~100 kPa;实验室环境下,柔性压力传感器与线性微位移传感器输出值之间的决定系数为0.9551;温室环境下,充分灌溉组中柔性压力传感器与线性微位移传感器输出值变化趋势一致,两者之间的决定系数为0.7672,亏缺灌溉组中两类传感器输出值均因水分亏缺而呈现下降趋势,输出值之间的决定系数为0.8519。本文所设计的柔性可穿戴压力传感器不仅能够实时监测番茄茎秆的膨胀和收缩变化,还可以对番茄亏水胁迫进行诊断,为实现高效节水灌溉提供重要的技术支撑。

摘要：规范HG/T21629中W1碟簧减振支架广泛应用于存在振动风险管道的支撑,在实际的静态应力分析过程中,设计人员一般将此类支架在CAESARII中建模为上下压紧的Y型约束和无间隙的导向约束组合,这种组合仅仅考虑了管道以及介质重量的摩擦,忽略了碟簧预紧摩擦力的影响,会对计算结果造成很大的影响。本文主要针对这一问题,讨论如何采用CAESARII中平移双作用双线性支架对W1型碟簧减振支架进行准确模拟,其中,对预紧摩擦力,建议按照动态荷载的大小、碟簧的适用范围以及摩擦系数进行选取,设计说明中应增加对安装的要求,确保预紧力的准确。在实例模拟中,分别采用考虑预紧摩擦力和未考虑预紧摩擦力两种方法进行计算,通过对其荷载和位移进行比较,建议使用W1型减振支架时,要将由于管道热胀对支架产生的摩擦轴向推力作为结构设计荷载予以考虑。

摘要：A process parameter optimization method for mold wear during die forging process is proposed and a mold life prediction method based on polynomial fitting is presented,by combining the variance analysis method in the orthogonal test with the finite element simulation test in the forging *** process parameters with the greatest influence on the mold wear during the die forging process and the optimal solution of the process parameters to minimize the wear depth of the mold are *** hot die forging process is taken as an example,and a mold wear correction model for hot forging processes is derived based on the Archard wear *** element simulation analysis of die wear process in hot die forging based on deform software is performed to study the relationship between the wear depth of the mold working surface and the die forging process parameters during hot forging *** optimized process parameters suitable for hot forging are derived by orthogonal experimental design and analysis of *** average wear amount of the mold during the die forging process is derived by calculating the wear depth of a plurality of key nodes on the mold *** life for the entire production process is predicted based on average mold wear depth and polynomial fitting.

摘要：局域少数点位的变形监测往往难以反馈复杂柔性防护系统的实际工作形态,常造成预警误报,为此提出了基于多点分布式的柔性防护系统变形视觉采集分析方法。利用帧间光流算法实现了落石冲击下柔性防护网系统全场二维速度场识别,据此建立了速度幅值二维分布图,通过相邻帧图像的速度分布差值图实现了柔性防护系统全场冲击变形状态的实时追踪,进一步提出了复杂运动叠加情形下柔性防护网系统稠密测点变形高鲁棒性提取算法,并分析了其变形规律同时提取了最大变形量,实现了有限测点监测到无限分布式传感的突破。设计了三跨柔性防护系统足尺模型,开展了750 kJ落石冲击试验,通过高速相机非接触式监测了落石冲击防护系统全过程影像数据。研究表明:所提议方法实现了落石冲击下柔性防护系统全场变形状态非接触、全历程追踪,冲击过程包含落锤接触防护系统、最大冲击变形与触底反弹三个阶段;为验证所提方法的可靠性,提取了落石冲击下柔性防护系统跨中区域冲击大变形曲线,发现750 kJ能量冲击下柔性防护系统的最大变形量为-6.201 m,与数值模拟和理论计算结果的相对误差分别为6.19%和0.93%。所提方法实现了足尺冲击试验中柔性防护系统工作形态的远程监测,有潜力应用于落石灾害下柔性防护系统的形态评价。

摘要：Loesses are widely distributed all over the world,especially in ***,long-term agricultural irrigation and extreme climate changes have led to frequent geological disasters in the Heifangtai area of Lanzhou,Gansu,*** these,landslides are one of the most frequent types of disasters that are harmful to humans and the environment.A landslide is closely related to the lithology,structure,and groundwater of the site and consists of a combination of structure units divided by discontinuities,such as faults,joints,and fi ***,geological surveys,engineering drilling,and trenching are typically used to identify the stratum lithology,structure,and groundwater in order to visually display underground information within a limited depth ***,these methods have *** particular,geological surveys can only describe geological phenomena on the surface,while the cost of drilling and trenching may be high,along with the ineffi ciency of *** this research,the integrated geophysical exploration method was used to analyze the hidden joints,cracks,and other discontinuities and geophysical features of the *** results were verified by trench exploration,and large amounts of underground information were obtained,especially the spread and distribution of discontinuities in landslide *** information can be effectively used for carrying out and providing meaningful experiences and lessons in future comprehensive geophysical processing and interpretations related to the prediction and evaluation of landslides.

摘要：新兴的智能超表面(Reconfigurable Intelligent Surface,RIS)技术作为6G潜在关键使能技术之一,通过大量的电磁单元智能调控无线信号的反射特性,有望实现对无线传播环境的主动增强与感知,其在角度感知估计方面的应用受到广泛关注。现有文献报道的RIS波达角估计硬件实现工作中,RIS往往采用固定列控或行控的编码方式,无法充分发挥其空间维度自由度,只能进行一维的波达角估计。在此背景下,本论文设计了一套灵活的智能超表面控制平台,实现对每个电磁单元的独立且高速的控制,充分发挥RIS硬件的空间自由度,并在此平台上实现基于RIS的二维波达角实时估计功能。首先,介绍基于RIS的波达角估计系统设计方案,通过对RIS进行高速空时编码调制,使反射信号的谐波分量与入射信号的波达角建立映射关系,在接收端利用反射信号各谐波的幅度和相位信息,对入射信号波达角进行实时估计。随后,基于所提方案设计系统的无线帧结构相关参数,构建基于RIS的二维波达角实时估计原型系统。最后,使用原型系统开展测量实验,在多个测量点位对波达角的方位角和俯仰角分量进行估计与数据记录,实测数据验证了所提方案的可行性。

摘要：The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different *** on the sliding-rolling mixed motion between ball and screw/nut raceway,the ball screw’s precision loss considering different given axial loading and rotational speed working conditions was *** creep and lubrication relate to sliding and rolling motion wear,the creep and lubrication characteristics are analyzed under different working ***,the precision loss was calculated considering the sole influence of sliding behavior between ball and screw and compared with the results from other current ***,research on precision loss owing to the sliding-rolling mixed motion behavior was realized under given working conditions,and suitable wear tests were carried *** analytical results of precision loss are in good agreement with the experimental test conclusions,which is conducive to better predicting the law of precision loss in stable wear period.

摘要：随着城市化进程的加快,城镇燃气管道建设日益受到关注。顶管施工技术作为一种高效、节省成本的施工方法,在燃气管道建设中具有广泛应用前景。本文通过对顶管施工技术的概念进行介绍,分析了城市建设中存在的问题,并在此基础上提出优化施工设施、引进先进技术、协调各部门分工工作以及严谨科学施工等策略,以改善燃气管道顶管施工的现状,确保施工质量和安全。

摘要：针对特种焊丝用钢907A模铸用发热保温冒口的材质进行改良设计,并对冒口内不同位置钢液的温降进行数值模拟。结果显示,钢温从1580℃降至1522℃需要约41 min。将该材质的发热保温冒口套用于9炉907A钢的真空熔铸试验,浇注温度1640~1650℃,浇注速度375~400 kg/min,切除冒口后,铸锭锭身无二次缩孔,有效提高铸锭成材率;将铸锭冒口成分与浇注前钢液成分对比,未发现冒口套在使用过程中,会对合金成分和气体含量产生不利影响。

摘要：在车辆控制器硬件在环测试中常采用单一环境建立复杂被控模型,但是所建模型精度与计算实时性存在矛盾等问题。为解决该问题,对在联合仿真环境中构建复杂的所需模型进行了研究。该模型由使用Simulink建立发动机、液力变矩器、车辆动力学模型和自动换挡控制器模型和使用AMESim建立的离合器、行星齿轮、液压系统、液力缓速器模型共同组成。在Veristand中创建了模型在环仿真控制界面,基于Veristand进行了NEDC工况下的模型在环仿真。仿真结果表明:所建模型运行稳定,计算量小,能准确地输出车辆换挡过程中各路信号,为基于硬件在环的车辆控制器测试提供了研究基础。