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高速高压双圆弧斜齿齿轮泵空化抑制措施研究 被引量:6
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作者 董庆伟 朱景龙 +1 位作者 李阁强 李行 《液压气动与密封》 2023年第7期49-55,共7页
双圆弧斜齿齿轮泵在高速高压工况下其内部流场空化现象严重,对齿轮泵的性能产生不利影响。为抑制齿轮泵的空化,建立了双圆弧斜齿齿轮泵吸油腔近啮合区域压力数学模型,以该区域压力值最大为目标函数,利用遗传算法对其各个影响因素求最优... 双圆弧斜齿齿轮泵在高速高压工况下其内部流场空化现象严重,对齿轮泵的性能产生不利影响。为抑制齿轮泵的空化,建立了双圆弧斜齿齿轮泵吸油腔近啮合区域压力数学模型,以该区域压力值最大为目标函数,利用遗传算法对其各个影响因素求最优解,重新建立齿轮泵三维模型并设定模拟工况,利用动网格技术,通过PUMPLINX对齿轮泵内部流场的空化现象进行数值模拟,并分析了抑制空化后对齿轮泵的影响。结果表明:抑制空化后齿轮泵内部流场空化现象明显减小,齿轮泵的空化现象得到了有效的抑制,验证了吸油腔近啮合区域压力数学模型的正确性;相对于抑制空化前,抑制空化后的齿轮泵流量脉动和流量脉动率明显减小,泵出口流量脉动率减小了25.63%,泵出口平均流量提高了4.4 L/min,泵容积效率提高了10.04%,显著提高了双圆弧斜齿齿轮泵的性能。 展开更多
关键词 双圆弧斜齿齿轮泵 高速高压 遗传算法 空化抑制 数值模拟
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基于频控阵雷达的一种最差环境下干扰抑制
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作者 陶馨珂 廖艳苹 《应用科技》 CAS 2024年第5期228-234,共7页
为了解决频控阵雷达的距离与角度耦合特性,形成能量聚集的点状波束,并且提高频控阵雷达的抗干扰能力,需要考虑到自适应波束形成技术。为此,在频控阵雷达接收模型基础上,推导最小方差无失真响应(minimum variance distortionless respons... 为了解决频控阵雷达的距离与角度耦合特性,形成能量聚集的点状波束,并且提高频控阵雷达的抗干扰能力,需要考虑到自适应波束形成技术。为此,在频控阵雷达接收模型基础上,推导最小方差无失真响应(minimum variance distortionless response,MVDR)波束形成算法,形成点波束能量聚集效果,在干扰抑制的基础上,针对旁瓣较高的问题,提出一种最差性能优化算法(worst-case performance optimization,WCP)的凸优化改进方法,形成点波束的同时降低旁瓣能量并且进行干扰抑制。区别于传统频偏优化的点波束形成方法与MVDR算法,通过在角度维度与距离维度上的独立分析发现,改进的方法可以在角度维与距离维降低旁瓣能量,干扰抑制效果更好。将该算法分别在均匀线阵和圆形频控阵中应用,圆形阵列增加了一个俯仰角维度,更适用于工程实际应用。 展开更多
关键词 频控阵 点波束形成 最小方差无失真响应算法 凸优化 干扰抑制 圆形阵列 最差性能优化算法 自适应波束
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Accurate Registration of Remote Sensing Images Based on Local Optimal Transformation
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作者 Bo Wang Changqing Li +2 位作者 Shi Tang Zhiqiang Zhou Hong Zhao 《Journal of Beijing Institute of Technology》 EI CAS 2019年第2期371-382,共12页
As the basic work of image stitching and object recognition,image registration played an important part in the image processing field.Much previous work in registration accuracy and realtime performance progressed ver... As the basic work of image stitching and object recognition,image registration played an important part in the image processing field.Much previous work in registration accuracy and realtime performance progressed very slowly,especially in registrating images with line feature.An innovative method for image registration based on lines is proposed,it can effectively improve the accuracy and real-time performance of image registration.The line feature can deal with some registration problems where point feature does not work.Our registration process is divided into two parts.The first part determines the rough registration transformation relation between reference image and test image.Then the similarity degree among different transformation and modified nonmaximum suppression(MNMS)algorithms are obtained,which produce local optimal solution to optimize the rough registration transformation.The final optimal registration relation can be obtained from two registration parts according to the match scores.The experimental results show that the proposed method makes a more accurate registration relation and performs better in real-time situation. 展开更多
关键词 initial REGISTRATION RELATIONSHIP accurate REGISTRATION RELATIONSHIP SIMILARITY DEGREE local optimal TRANSFORMATION modified non-maximum suppression(MNMS)algorithm
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YOLO-Banana:An Effective Grading Method for Banana Appearance Quality
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作者 Dianhui Mao Xuesen Wang +3 位作者 Yiming Liu Denghui Zhang Jianwei Wu Junhua Chen 《Journal of Beijing Institute of Technology》 EI CAS 2023年第3期363-373,共11页
The increasing trend towards independent fruit packaging demands a high appearance quality of individually packed fruits.In this paper,we propose an improved YOLOv5-based model,YOLO-Banana,to effectively grade banana ... The increasing trend towards independent fruit packaging demands a high appearance quality of individually packed fruits.In this paper,we propose an improved YOLOv5-based model,YOLO-Banana,to effectively grade banana appearance quality based on the number of banana defect points.Due to the minor and dense defects on the surface of bananas,existing detection algorithms have poor detection results and high missing rates.To address this,we propose a densitybased spatial clustering of applications with noise(DBSCAN)and K-means fusion clustering method that utilizes refined anchor points to obtain better initial anchor values,thereby enhancing the network’s recognition accuracy.Moreover,the optimized progressive aggregated network(PANet)enables better multi-level feature fusion.Additionally,the non-maximum suppression function is replaced with a weighted non-maximum suppression(weighted NMS)function based on distance intersection over union(DIoU).Experimental results show that the model’s accuracy is improved by 2.3%compared to the original YOLOv5 network model,thereby effectively grading the banana appearance quality. 展开更多
关键词 YOLOv5 banana appearance grading clustering algorithm weighted non-maximum suppression(weighted NMS) progressive aggregated network(PANet)
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Sub-Window尺度空间的Attention-HardNet特征匹配算法 被引量:3
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作者 齐向明 冯一帆 《激光与光电子学进展》 CSCD 北大核心 2021年第22期142-153,共12页
为保护尺度空间边缘和角点信息,提高特征匹配算法的可靠性,提出一种Sub-Window尺度空间的Attention-HardNet特征匹配算法。该算法通过Sub-window box filter构建尺度空间来充分保留尺度空间图像边缘及角点信息;使用FAST算法提取尺度空... 为保护尺度空间边缘和角点信息,提高特征匹配算法的可靠性,提出一种Sub-Window尺度空间的Attention-HardNet特征匹配算法。该算法通过Sub-window box filter构建尺度空间来充分保留尺度空间图像边缘及角点信息;使用FAST算法提取尺度空间特征点来提高特征点提取速度,再利用圆形非极大值抑制算法对其进行优化,提高准确率;对HardNet特征提取网络添加SENet注意力机制,构成Attention-HardNet,提取鲁棒性更强的128维浮点型特征描述符,最后利用L2距离衡量不同描述符的相似性,完成图像特征点匹配。在Oxford数据集上对匹配算法抗尺度、压缩、光照等性能进行测试,由测试结果可以看出本文算法相较于常用匹配算法,匹配正确率得到较大提升,相较于L2net、HardNet等深度学习方法,匹配正确率提高3%左右,速度约提高10%。 展开更多
关键词 图像处理 sub-window尺度空间 圆形非极大值抑制算法 HardNet SENet注意力机制
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