摘要：Disturbance in wind regime and sand erosion deposition balance may lead to burial and eventual vanishing of a *** study conducted 3D computational fluid dynamics(CFD)simulations to evaluate the effect of a proposed city design on the wind environment of the Crescent Spring,a downwind natural heritage site located in Dunhuang,Northwestern *** terrain data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)Digital Elevation Model(DEM)were used to construct the solid surface ***-state Reynolds Averaged Navier-Stokes equations(RANS)with shear stress transport(SST)k-ωturbulence model were then applied to solve the flow field ***-use changes were modeled implicitly by dividing the underlying surface into different areas and by applying corresponding aerodynamic roughness *** were performed by using cases with different city areas and building *** show that the selected model could capture the surface roughness changes and could adjust wind profile over a large *** profiles varied over the greenfield to the north and over the Gobi land to the east of the ***,different wind speed reduction effects were observed from various city construction *** current city design would lead to about 2 m/s of wind speed reduction at the downwind city edge and about 1 m/s of wind speed reduction at the north of the spring at 35-m *** the city height in the north greenfield area could efficiently eliminate the negative effects of wind *** contrast,restricting the city area worked better in the eastern Gobi area compared with other parts of the study *** speed reduction in areas near the spring could be limited to 0.1 m/s by combining these two abatement *** CFD method could be applied to simulate the wind environment affected by other land-use changes over a large terrain.

摘要：为了预防煤矿作业中因个人防护装备缺失导致的安全事故,提升工人安全帽和安全背心佩戴情况的智能检测能力。基于YOLOv8提出1种改进的目标检测算法SMT-YOLOv8s,该算法引入尺度感知调制模块(scale-aware modulation transformer,SMT)用于增强图像特征提取,设计跨通道增强通道注意力模块(cross-channel enhanced channel attention,C2ECA)以突出目标特征的表征能力,并提出增强型完全交并比(improved enhanced complete intersection over union,IE-CIoU),用于更精确地计算预测框与真实框之间的位置偏差。研究结果表明:提出的SMT-YOLOv8s算法相较于YOLOv8s模型在自建数据集上的mAP50和mAP50-95分别提高3.7百分点和2.7百分点。与其他算法相比,SMT-YOLOv8s兼具较高精度和计算效率。研究结果可为煤矿个人防护装备智能检测研究提供参考。

摘要：传统齿轮传动存在空回和间隙等问题,难以满足光电系统高精密传动的需求。在分析了钢丝绳和钢带传动技术特点的基础上,设计了一种基于钢丝绳传动的潜望镜用1:1测角机构,以及一种基于钢带传动的光电系统用2:1传动机构。基于光学测量的方法,采用旋变测量了钢丝绳传动机构的传动误差,采用经纬仪测量了钢带传动机构的传动误差。结果显示钢丝绳传动精度可达到分级,在-110°+135°的范围内转角误差小于3.5′;钢带传动精度可达到秒级,在-3°^+3°的范围内转角误差小于11.9″,满足了潜望镜和某光电系统性能指标要求。

摘要：制动器摩擦试验机是用来检测汽车刹车片的各项性能参数的,温度对其影响非常大。传统的测试系统构成比较复杂且采集到的数据分析针对性不够等。针对这一现状,基于一台新型(便携式)汽车制动器摩擦试验机设计其温度采集系统,借助Labview软件平台,实现多通道实时测控并进行温度数据采集与查询,可通过Access直接导出数据,便于分析。该系统解决了目前测量精度低、稳定性弱、检测指标针对性不强等问题,结合测试系统的基本原理,为提高测量精度,实现系统输入-输出的理想曲线关系提供了一定的研究价值。