In ghost imaging, an illumination light is split into test and reference beams which pass through two different optical systems respectively and an image is constructed with the second-order correlation between the tw...In ghost imaging, an illumination light is split into test and reference beams which pass through two different optical systems respectively and an image is constructed with the second-order correlation between the two light beams. Since both light beams are diffracted when passing through the optical systems, the spatial resolution of ghost imaging is in general lower than that of a corresponding conventional imaging system. When Gaussian-shaped light spots are used to illuminate an object, randomly scanning across the object plane, in the ghost imaging scheme, we show th√at by localizing central positions of the spots of the reference light beam, the resolution can be increased by a factor of 2^(1/2) same as that of the corresponding conventional imaging system. We also find that the resolution can be further enhanced by setting an appropriate threshold to the bucket measurement of ghost imaging.展开更多
数据流是一类具有高生成率、动态分布特性的数据,其异常检测旨在从这一类数据中发现偏离预期行为的数据流,从而为医疗、工业生产、金融等诸多领域的决策提供支持。现有数据流异常检测方法普遍面临参数敏感性高、时空开销大、阈值选取难...数据流是一类具有高生成率、动态分布特性的数据,其异常检测旨在从这一类数据中发现偏离预期行为的数据流,从而为医疗、工业生产、金融等诸多领域的决策提供支持。现有数据流异常检测方法普遍面临参数敏感性高、时空开销大、阈值选取难等问题。为了解决上述问题,提出一种基于变密度的自适应数据流的异常检测方法。首先定义了可变局部离群因子(Va-riable Local Outlier Factor,VLOF),VLOF通过对比数据点在并行的不同k值的邻域窗口下,其局部可达密度和局部异常因子的变化情况,度量数据点的密度分布,降低单一k近邻密度度量导致的结果不准确。其次,计算VLOF与k值的相对增长率和绝对均值率,以反映数据流的动态变化趋势,并将适应这种动态变化趋势的数据点定义为核心点,通过核心点加快对后续正常点的判断。最后,将相对增长率和绝对均值率作为数据点理论分布的度量指标,计算理论分布和新数据点实际分布的差异,从而自适应地将偏离理论分布的点识别为异常。为了验证提出算法的有效性,在多个UCI数据集和真实数据集下与8个算法进行对比实验,实验结果表明:与基线模型相比,所提方法在精确率、召回率、F1性能指标上表现良好,且时间和空间效率也有相应提升。展开更多
A so-called 'local probabilistic Paris relation method' was presented for measuring the random thresholds of long fatigue crack propagation. A check was made to the conventional method, in which the thresholds...A so-called 'local probabilistic Paris relation method' was presented for measuring the random thresholds of long fatigue crack propagation. A check was made to the conventional method, in which the thresholds were measured statistically and directly by the test data. It was revealed that this method was not reasonable because the test data have seldom a unified level of crack growth rates. Differently,in the presented method the Paris-Erdogan equation was applied to model the local test data around the thresholds. Local probabilistic relations with both the survival probability and the confidence were established on a lognormal distribution of the stress density factors. And then, the probabilistic thresholds were derived from the probabilistic factors with a given critical level of growth rate. An analysis on the test data of LZ50 axle steel for the Chinese railway vehicles verifies that the present method is feasible and available.展开更多
This review hopes to clearly explain the following viewpoints： （1） Neuronal synchronization underlies brain functioning, and it seems possible that blocking excessive synchronization in an epileptic neural network ...This review hopes to clearly explain the following viewpoints： （1） Neuronal synchronization underlies brain functioning, and it seems possible that blocking excessive synchronization in an epileptic neural network could reduce or even control seizures. （2） Local field potential coupling is a very common phenomenon during synchronization in networks. Removal of neurons or neuronal networks that are coupled can significantly alter the extracellular field potential. Interventions of coupling mediated by local field potentials could result in desynchronization of epileptic seizures. （3） The synchronized electrical activity generated by neurons is sensitive to changes in the size of the extracellular space, which affects the efficiency of field potential transmission and the threshold of cell excitability. （4） Manipulations of the field potential fluctuations could help block synchronization at seizure onset.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11534008,11605126,and 11804271)the Fund from the Ministry of Science and Technology of China(Grant No.2016YFA0301404)+2 种基金the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.2017JQ1025)the Doctoral Fund of the Ministry of Education of China(Grant Nos.2016M592772 and 2018M631137)the Fundamental Research Funds for the Central Universities
文摘In ghost imaging, an illumination light is split into test and reference beams which pass through two different optical systems respectively and an image is constructed with the second-order correlation between the two light beams. Since both light beams are diffracted when passing through the optical systems, the spatial resolution of ghost imaging is in general lower than that of a corresponding conventional imaging system. When Gaussian-shaped light spots are used to illuminate an object, randomly scanning across the object plane, in the ghost imaging scheme, we show th√at by localizing central positions of the spots of the reference light beam, the resolution can be increased by a factor of 2^(1/2) same as that of the corresponding conventional imaging system. We also find that the resolution can be further enhanced by setting an appropriate threshold to the bucket measurement of ghost imaging.
文摘数据流是一类具有高生成率、动态分布特性的数据,其异常检测旨在从这一类数据中发现偏离预期行为的数据流,从而为医疗、工业生产、金融等诸多领域的决策提供支持。现有数据流异常检测方法普遍面临参数敏感性高、时空开销大、阈值选取难等问题。为了解决上述问题,提出一种基于变密度的自适应数据流的异常检测方法。首先定义了可变局部离群因子(Va-riable Local Outlier Factor,VLOF),VLOF通过对比数据点在并行的不同k值的邻域窗口下,其局部可达密度和局部异常因子的变化情况,度量数据点的密度分布,降低单一k近邻密度度量导致的结果不准确。其次,计算VLOF与k值的相对增长率和绝对均值率,以反映数据流的动态变化趋势,并将适应这种动态变化趋势的数据点定义为核心点,通过核心点加快对后续正常点的判断。最后,将相对增长率和绝对均值率作为数据点理论分布的度量指标,计算理论分布和新数据点实际分布的差异,从而自适应地将偏离理论分布的点识别为异常。为了验证提出算法的有效性,在多个UCI数据集和真实数据集下与8个算法进行对比实验,实验结果表明:与基线模型相比,所提方法在精确率、召回率、F1性能指标上表现良好,且时间和空间效率也有相应提升。
基金Project supported by the National Natural Science Foundation of China (Nos. 50375130 and 50323003)the Special Foundation for the Authors of National Excellent Doctoral Disserta tions (No. 200234)the Outstanding Young Teachers Program of State Education Ministry (No. 2101)
文摘A so-called 'local probabilistic Paris relation method' was presented for measuring the random thresholds of long fatigue crack propagation. A check was made to the conventional method, in which the thresholds were measured statistically and directly by the test data. It was revealed that this method was not reasonable because the test data have seldom a unified level of crack growth rates. Differently,in the presented method the Paris-Erdogan equation was applied to model the local test data around the thresholds. Local probabilistic relations with both the survival probability and the confidence were established on a lognormal distribution of the stress density factors. And then, the probabilistic thresholds were derived from the probabilistic factors with a given critical level of growth rate. An analysis on the test data of LZ50 axle steel for the Chinese railway vehicles verifies that the present method is feasible and available.
基金supported by grants from the National Natural Science Foundation of China,No. 30971534125 Project of the Third Xiangya Hospital of Central South University,China
文摘This review hopes to clearly explain the following viewpoints： （1） Neuronal synchronization underlies brain functioning, and it seems possible that blocking excessive synchronization in an epileptic neural network could reduce or even control seizures. （2） Local field potential coupling is a very common phenomenon during synchronization in networks. Removal of neurons or neuronal networks that are coupled can significantly alter the extracellular field potential. Interventions of coupling mediated by local field potentials could result in desynchronization of epileptic seizures. （3） The synchronized electrical activity generated by neurons is sensitive to changes in the size of the extracellular space, which affects the efficiency of field potential transmission and the threshold of cell excitability. （4） Manipulations of the field potential fluctuations could help block synchronization at seizure onset.
