共查询到10条相似文献,搜索用时 93 毫秒
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N. V. Mayko 《Cybernetics and Systems Analysis》2017,53(1):83-91
We obtain improved accuracy estimates of the finite-difference scheme for a two-dimensional parabolic equation in a unit square, considering the effect of the Dirichlet boundary condition and the initial condition. We prove that the accuracy order is higher near the sides and the bottom of the space-time parallelepiped. 相似文献
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针对目前在遥感目标检测领域广泛使用的YOLOv3算法存在对小目标物体的特征表达能力不足,检测效果不好的问题,本文提出一种改进的YOLOv3小目标检测算法.首先,引入全局信息注意力机制并改进特征提取网络和特征金字塔结构,提高模型小目标特征提取能力和检测能力;其次,对数据集进行单尺度Retinex融合特征增强,提高模型对小目标特征的学习效果;最后,使用自适应锚框优化算法对anchors进行优化,提高anchors和目标的匹配程度.选用遥感数据集RSOD进行实验,本文算法的全类平均精度为92.5%,相比经典YOLOv3算法,提高10.1%,对遥感小目标的检测效果得到明显提升. 相似文献
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Learning Conjunctive Concepts in Structural Domains 总被引:6,自引:6,他引:0
We study the problem of learning conjunctive concepts from examples on structural domains like the blocks world. This class of concepts is formally defined, and it is shown that even for samples in which each example (positive or negative) is a two-object scene, it is NP-complete to determine if there is any concept in this class that is consistent with the sample. We demonstrate how this result affects the feasibility of Mitchell's version of space approach and how it shows that it is unlikely that this class of concepts is polynomially learnable from random examples alone in the PAC framework of Valiant. On the other hand, we show that for any fixed bound on the number of objects per scene, this class is polynomially learnable if, in addition to providing random examples, we allow the learning algorithm to make subset queries. In establishing this result, we calculate the capacity of the hypothesis space of conjunctive concepts in a structural domain and use a general theorem of Vapnik and Chervonenkis. This latter result can also be used to estimate a sample size sufficient for heuristic learning techniques that do not use queries. 相似文献
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支持向量机是一种基于结构风险最小化原理的学习技术,也是一种新的具有很好泛化性能的回归方法。目前,如何设计快速有效的回归估计算法仍然是支持向量机实际应用中的问题之一。文中对标准SVM回归估计算法加以改进,提出一种改进的SVM回归估计算法,并从学习速度和回归估计精度两个方面对提出的改进的SVM回归估计算法与标准SVM回归估计算法进行了比较。实验结果表明,在学习速度与回归估计精度之间取折衷时,文中提出的回归估计算法自由度更大。 相似文献
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重跟踪处理可以从雷达高度计接收的海洋回波信号中提取精确的测量信息,传统的海洋高度计重跟踪模型中没有考虑到仪器对回波信号的影响,这种影响造成回波波形与重跟踪模型的偏离,从而降低了重跟踪的参数提取精度。提出了一种利用点目标响应和加权窗进行海洋高度计重跟踪的新方法,该方法考虑了仪器对回波波形的影响因素,在此基础上重新构造了重跟踪的信号模型,使回波波形与重跟踪模型曲线之间符合更好,从而提高了参数提取的精度。利用该方法对SZ-4高度计的数据进行了处理,并将处理结果与同期测量的ERS-2高度计数据进行对比,对比结果显示该方法显著改善了参数提取的效果。 相似文献