MHD mixed convection of a Cu–water nanofluid flow through a channel with an open trapezoidal cavity and an elliptical obstacle

In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nu_avg rises as the Ri rise, the maximum Nu_avg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nu_avg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05).     

基于深度学习的四旋翼无人机单目视觉避障方法

针对无人机避障问题，提出一种基于深度学习的四旋翼无人机单目视觉避障方法。首先通过目标检测框选出目标在图像中的位置，并通过计算目标选框上下边距的长度，以此来估量出障碍物到无人机之间的距离；然后通过协同计算机判断是否执行避障动作；最后使用基于Pixhawk搭建的飞行实验平台进行实验。实验结果表明，该方法可用于无人机低速飞行条件下避障。该方法所用到的传感器只有一块单目摄像头，而且相对于传统的主动式传感器避障方法，所占用无人机的体积大幅减小。该方法鲁棒性较好，能够准确识别不同姿态的人，实现对人避障。     

煤矿地面轨道运输矿车自动避障技术研究

介绍了煤矿地面轨道运输矿车自动避障技术。首先介绍了基于雷达的矿车前方障碍物检测技术及其相关算法,然后详细介绍了基于机器视觉的矿车前方障碍物检测系统和常用的图像处理方法以及相关的算法,最后介绍了雷达和机器视觉融合的障碍物检测技术在煤矿地面轨道运输矿车自动避障过程中的应用。     

Cleaning of viscous drops on a flat inclined surface using gravity-driven film flows

We investigate the fluid mechanics of cleaning viscous drops attached to a flat inclined surface using thin gravity-driven film flows. We focus on the case where the drop cannot be detached either partially or completely from the surface by the mechanical forces exerted by the cleaning fluid on the drop surface. Instead a convective mass transfer establishes across the drop–film interface and the fluid in the drop dissolves into the cleaning film flow, which then transports it away. The characteristic time scale of dissolution is much longer than the advection time scale in the film flow. Thus, the shape and size of the drop can be considered as quasi-steady. To assess the impact of the shape and size of the drop on the velocity of the cleaning fluid, we have developed a novel experimental technique based on particle image velocimetry. We show the velocity distribution at the film surface in the situations both where the film is flowing over a smooth surface, and where it is perturbed by a solid obstacle representing a very viscous drop. We find that at intermediate Reynolds numbers the acceleration of the starting film is overestimated by a plane model using the lubrication approximation. In the perturbed case, the streamwise velocity is strongly affected by the presence of the obstacle. The upstream propagation of the disturbance is limited, but the disturbance extends downstream for distances larger than 10 obstacle diameters. Laterally, we observe small disturbances in both the streamwise and lateral velocities, owing to stationary capillary waves. The flow also exhibits a complex three-dimensional converging pattern immediately below the obstacle.     

化工园区应急响应阶段应急救援与疏散双向路径规划

应急救援与应急疏散是化工园区应急响应过程中的两类关键性决策。在实际的应急响应中,因园区路网简单、通行能力较弱等问题很可能出现道路冲突或拥堵的情况,导致疏散失败或救援车辆无法撤离。为解决上述问题,本文提出了一种考虑智能避障的化工园区应急救援与应急疏散双向路径优化方法。构建了基于动态栅格的环境模型,针对园区内部应急响应与园区内外协同应急响应两个阶段,分别定义了不同应急响应阶段下园区内的应急救援agent、应急疏散agent、园区外进入园区的应急救援agent和园区内离开园区的应急救援agent四类agent的结构与移动规则。针对化工园区应急响应两个阶段的响应特性,提出两种智能避障模型用以避免道路冲突,建立考虑智能避障的化工园区应急响应两阶段应急救援与应急疏散双向路径规划模型。采用动态栅格法对化工园区栅格环境进行实时更新,应用Dijkstra算法对化工园区双向应急救援与应急疏散路径进行仿真优化。仿真实验结果表明,应用所提出的优化方法可分别得到化工园区应急响应两个阶段无冲突的最优双向路径,实现智能避障前提下的双向路径最短,具有较高可行性与实用价值。     

楼梯升降机简介

介绍楼梯升降机的结构、参数、特点、具体应用和选购指南。     

基于MSP430的小车式灭火机器人设计

本设计是以MSP430F149单片机为核心的小车式灭火报警机器人,通过红外火焰传感器的数字输出进行火源寻找,并根据采集到的信号对行进方向进行调整,同时利用红外对管实现机器人避障。机器人行进过程中能够依据火焰传感器的模拟量输出估算出机器人与火源之间的距离,并利用MQ 2烟雾浓度传感器检测周围烟雾浓度。此外本设计具有液晶显示功能、蜂鸣器报警功能以及LED灯光报警功能。整体设计低能耗、低成本,实验表明：小车式机器人能够快速有效的寻找到火源,并进行灭火,适用于家庭、宿舍、加油站等小型场所。     

地下铲运机自主行驶与避障控制方法研究

由测量数据或轨迹推算模型,计算铲运机横向位置偏差、航向角偏差及航向角偏差变化率,三偏差通过非线性融合规则,形成融合偏差反馈信号并作为PID校正控制的输入量,设置横向位置偏差及航向角偏差双门限值来改进PID算法。该自主行驶控制方法在轨迹偏差及行驶车速大范围变化时,仍能保持优良的稳定性和快速性。     

Effect of obstacle strength and spacing on the slope of Haasen plot

The rate sensitivity of multiple obstacle aluminium alloy system was measured using the stress relaxation method. A discrepancy was observed between the slope of the Haasen plot (rate sensitivity of dislocation–dislocation interaction) in pure metals and in alloys strengthened by multiple obstacles. Considering a simplifying assumption of the constant obstacle force–distance profile, it is suggested that slope of the Haasen plot is governed by glide dislocations’ length taking part in a thermally activated event. The relative strength and spacing of obstacles (forest dislocations, solutes and precipitates) is proposed to affect the thermally activated dislocation length, which in turn manifests as the difference in slope of the Haasen plot.     

基于透视投影的激光跟踪测量系统可视性分析

针对现有激光跟踪测量系统可视性分析方法在计算效率方面的不足，提出一种基于透视投影的激光跟踪测量系统可视性分析方法。给出了激光跟踪仪可视性分析的数学定义，利用测点与站位点之间的关系对可视性分析进行描述；利用包络盒对障碍物进行简化，同时根据障碍物、测点、站位点之间的关系，剔除了不参与可视性分析运算的障碍物；在此基础上，利用透视投影的原理，对障碍物在跟踪仪可布置平面上的投影进行了求解，并利用该投影与站位点之间是否包含的关系，得到了测点与站位点之间的可视性矩阵，结合提出的可视性势能的概念，对跟踪仪满足可视性的区域进行了求解。最后，以某飞机舱门检验工装的测量为例，验证了该方法和模型的正确性和有效性。