针对秧苗列中心线的检测结果易受到水田中的浮萍、蓝藻以及水面反射、风速、光照情况等自然条件影响的问题,提出一种基于YOLOv3目标检测的秧苗列中心线检测算法。基于透视投影计算提取图像的ROI(Region of interest)区域,采用ROI图像构...针对秧苗列中心线的检测结果易受到水田中的浮萍、蓝藻以及水面反射、风速、光照情况等自然条件影响的问题,提出一种基于YOLOv3目标检测的秧苗列中心线检测算法。基于透视投影计算提取图像的ROI(Region of interest)区域,采用ROI图像构建数据集,对YOLOv3模型进行训练,训练过程中通过减少YOLOv3模型的输出降低运算量,利用模型识别定位ROI内的秧苗,并输出其检测框,对同列秧苗的检测框进行自适应聚类。在对秧苗图像进行灰度化和滤波处理后,在同类检测框内提取秧苗SUSAN(Smallest univalue segment assimilating nucleus)角点特征,采用最小二乘法拟合秧苗列中心线。试验结果表明,该算法对于秧苗的不同生长时期,以及在大风、蓝藻、浮萍和秧苗倒影、水面强光反射、暗光线的特殊场景下均能成功提取秧苗列中心线,鲁棒性较好,模型的平均精度为91.47%,提取的水田秧苗列中心线平均角度误差为0.97°,单幅图像(分辨率640像素×480像素)在GPU下的平均处理时间为82.6 ms,能够满足视觉导航的实时性要求。为复杂环境下作物中心线的提取提供了有效技术途径。展开更多
复杂场景下小目标检测是目标检测领域的研究难点和热点。传统的two-stage和one-stage检测模型都是通过预先设定锚点框与真实目标框的交并比(intersection over union,IoU)阈值来划分正负样本集,同时这组预定义的固定锚点框还用于获取候...复杂场景下小目标检测是目标检测领域的研究难点和热点。传统的two-stage和one-stage检测模型都是通过预先设定锚点框与真实目标框的交并比(intersection over union,IoU)阈值来划分正负样本集,同时这组预定义的固定锚点框还用于获取候选框,进而得到检测结果。然而,在复杂场景下,预先设定的IoU阈值会带来正负样本不均衡问题;针对小尺寸目标(船舶)检测,预定义的锚点框也很难保证覆盖目标的位置和密度,因此限制了检测模型的准确率。为了解决上述问题,提出自适应锚点框(adaptive anchor boxes,AAB)的方法优化目标检测网络,采用基于形状相似度距离的聚类算法生成锚点框,提高目标区域定位技术;采用利用聚类的锚点框计算自适应IoU阈值(adaptive threshold selection,ATS),划分正负样本,保证样本均衡。对复杂场景下的小目标(船舶目标)进行检测,实验结果表明,采用自适应锚点框方法和自适应阈值选择方法的目标检测模型在复杂场景中检测均能提升准确,对比faster R-CNN、FPN、Yolo3和pp-Yolo,融合了上述新方法的模型均提升了检测准确率,分别提升了9.6、2.6、9.8和9.9个百分点。展开更多
The effects of exercise on decision-making performance have been studied using a wide variety of cognitive tasks and exercise interventions. Although the current literature supports a beneficial influence of acute exe...The effects of exercise on decision-making performance have been studied using a wide variety of cognitive tasks and exercise interventions. Although the current literature supports a beneficial influence of acute exercise on cognitive performance, the mechanisms underlying this phenomenon have not yet been elucidated. We review studies that used single-pulse transcranial magnetic stimulation （TMS） to probe the excitability of motor structures during whole-body exercise and present a framework to account for the facilitating effects of acute exercise on motor processes. Recent results suggest that, even in the absence of fatigue, the increase in corticospinal excitability classically reported during submaximal and exhausting exercises may be accompanied by a reduction in intracortical inhibition. We propose that reduced intracortical inhibition elicits an adaptive central mechanism that counteracts the progressive reduction in muscle responsiveness caused by peripheral fatigue. Such a reduction would render the motor cortex more sensitive to upstream influences, thus causing increased corticospinal excitability. Furthermore, reduction of intracortical inhibition may account for the more efficient descending drive and for the improvement of reaction time performance during exercise. The adaptive modulation in intracortical inhibition could be implemented through a general increase in reticular activation that would further account for enhanced sensory sensitivity.展开更多
The purpose of this paper is to improve allocation of the number of bits without skipping the frame by accurately estimating the target bits in H. 264/AVC rate control. The scheme ImPoses an enhancement method of the ...The purpose of this paper is to improve allocation of the number of bits without skipping the frame by accurately estimating the target bits in H. 264/AVC rate control. The scheme ImPoses an enhancement method of the target frame rate based on H. 264/AVC bit allocation. The enhancement uses a frame complexion estimation to improve the existing Mean Absolute Difference （MAD） complexity measurement. Bit allocation to each frame is not just computed by target frame rote but also adjusted by a combined frame complexity measure. Using the statistical characteristic, the scheme obtains change of occurrence bit about QP to apply the bit amount by QP from the video characteristic and apply it in the estimated bit amount of the current frame. Simulation results show that the proposed rate eontrol scheme achieves time saving of mine than 99% over existing rate control algorithm. Nevertheless, Peak Signal-to-Noise Ration （PSNR） and bit rate were almost the same as the performances.展开更多
This paper adopts the concept of dynamic feedback systems to model the behavior of financial markets, or more specifically, the stock market from a dynamic system point of view. Based on a feedback adaptation scheme, ...This paper adopts the concept of dynamic feedback systems to model the behavior of financial markets, or more specifically, the stock market from a dynamic system point of view. Based on a feedback adaptation scheme, the authors model the movement of a stock market index within a framework that is composed of an internal dynamic model and an adaptive filter. The output-error model is adopted as the internal model whereas the adaptive filter is a time-varying state space model with instrumental variables. Its input-output behavior, and internal as well as external forces are then identified. Special attention has also been paid to the recent financial crisis by examining the movement of Dow Jones Industrial Average （DJIA） as an example to illustrate the advantage of the proposed framework. Supported by time-varying causality tests, five influential factors from economic and sentiment aspects are introduced as the input of this framework. Testing results show that the proposed framework has a much better prediction performance than the existing methods, especially in complicated economic situations. An application of this framework is also presented with focuses on forecasting the turning periods of the market trend. Realizing that a market trend is about to change when the external force begins to exhibit clear patterns in its frequency responses, the authors develop a set of rules to recognize this kind of clear patterns. These rules work well for stock indexes from US, China and Singapore.展开更多
文摘The effects of exercise on decision-making performance have been studied using a wide variety of cognitive tasks and exercise interventions. Although the current literature supports a beneficial influence of acute exercise on cognitive performance, the mechanisms underlying this phenomenon have not yet been elucidated. We review studies that used single-pulse transcranial magnetic stimulation （TMS） to probe the excitability of motor structures during whole-body exercise and present a framework to account for the facilitating effects of acute exercise on motor processes. Recent results suggest that, even in the absence of fatigue, the increase in corticospinal excitability classically reported during submaximal and exhausting exercises may be accompanied by a reduction in intracortical inhibition. We propose that reduced intracortical inhibition elicits an adaptive central mechanism that counteracts the progressive reduction in muscle responsiveness caused by peripheral fatigue. Such a reduction would render the motor cortex more sensitive to upstream influences, thus causing increased corticospinal excitability. Furthermore, reduction of intracortical inhibition may account for the more efficient descending drive and for the improvement of reaction time performance during exercise. The adaptive modulation in intracortical inhibition could be implemented through a general increase in reticular activation that would further account for enhanced sensory sensitivity.
文摘The purpose of this paper is to improve allocation of the number of bits without skipping the frame by accurately estimating the target bits in H. 264/AVC rate control. The scheme ImPoses an enhancement method of the target frame rate based on H. 264/AVC bit allocation. The enhancement uses a frame complexion estimation to improve the existing Mean Absolute Difference （MAD） complexity measurement. Bit allocation to each frame is not just computed by target frame rote but also adjusted by a combined frame complexity measure. Using the statistical characteristic, the scheme obtains change of occurrence bit about QP to apply the bit amount by QP from the video characteristic and apply it in the estimated bit amount of the current frame. Simulation results show that the proposed rate eontrol scheme achieves time saving of mine than 99% over existing rate control algorithm. Nevertheless, Peak Signal-to-Noise Ration （PSNR） and bit rate were almost the same as the performances.
文摘This paper adopts the concept of dynamic feedback systems to model the behavior of financial markets, or more specifically, the stock market from a dynamic system point of view. Based on a feedback adaptation scheme, the authors model the movement of a stock market index within a framework that is composed of an internal dynamic model and an adaptive filter. The output-error model is adopted as the internal model whereas the adaptive filter is a time-varying state space model with instrumental variables. Its input-output behavior, and internal as well as external forces are then identified. Special attention has also been paid to the recent financial crisis by examining the movement of Dow Jones Industrial Average （DJIA） as an example to illustrate the advantage of the proposed framework. Supported by time-varying causality tests, five influential factors from economic and sentiment aspects are introduced as the input of this framework. Testing results show that the proposed framework has a much better prediction performance than the existing methods, especially in complicated economic situations. An application of this framework is also presented with focuses on forecasting the turning periods of the market trend. Realizing that a market trend is about to change when the external force begins to exhibit clear patterns in its frequency responses, the authors develop a set of rules to recognize this kind of clear patterns. These rules work well for stock indexes from US, China and Singapore.
