The effect of rotation on the shape (figure) and gravitational quadrupole of astronomical bodies is calculated by using an approximate point core model: A point mass at the center of an ellipsoidal homogeneous fluid. ...The effect of rotation on the shape (figure) and gravitational quadrupole of astronomical bodies is calculated by using an approximate point core model: A point mass at the center of an ellipsoidal homogeneous fluid. Maclaurin’s analytical result for homogenous bodies generalizes to this model and leads to very accurate analytical results connecting the three observables: oblateness (ò), gravitational quadrupole (J2), and angular velocity parameter (q). The analytical results are compared to observational data for the planets and a good agreement is found. Oscillations near equilibrium are studied within the model.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
Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-cover...Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.展开更多
Using embedded atom method and molecular static relaxation method, the core structure of <100>, <110> edge dislocations, <100> screw dislocation, the interaction between point defects and <100>...Using embedded atom method and molecular static relaxation method, the core structure of <100>, <110> edge dislocations, <100> screw dislocation, the interaction between point defects and <100> edge dislocation in NiAl intermetallics were investigated. The results show that <100>edge dislocation expands along and orientation on the (001) slip plane. The core structure of <100> edge dislocation on (001) plane is like a 'butterfly', while it is very compact when it lies on {110} slip plane. So NiAl will have a <100>{110} slip system in stead of <100>{100} slip system, as experiments showed. <110> edge dislocation has a more expanded core structure and the atoms of dislocation core distort more heavily. None dislocation dissociation was found in the studied dislocations. The outlines of dislocation core structures change very little after a row of point defects are introduced in them, which can be explained by point defects' little effects on the stress field around dislocation core. The results also show that it is hard to change dislocation core structure by decreasing alloy order using the method of introducing limited point defects into the alloy.展开更多
在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(M...在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(Matern Hard Core Point Processes,MHCPP)对ISAC基站的位置分布进行建模,考虑通信和感知时分复用的系统机制,以典型用户作为研究对象,将其关联到距离最近的基站,分别对通信和感知进行性能指标建模,推导典型用户和关联基站受到的平均干扰功率以及平均吞吐量的下界,并进一步通过仿真验证推导结果的准确性.仿真结果表明:相较于泊松点过程(Poisson Point Processes,PPP),MHCPP对平均干扰功率具有降低效果,通信场景中平均干扰功率降低了30%~43%,感知场景中平均干扰功率降低了91%~93%;随着基站间最小距离的增大,通信平均吞吐量增加,感知平均吞吐量先增后减,在实际场景中需结合系统需求来确定ISAC组网的参数设计.研究结果可为系统设计和扩展性分析提供参考.展开更多
文摘The effect of rotation on the shape (figure) and gravitational quadrupole of astronomical bodies is calculated by using an approximate point core model: A point mass at the center of an ellipsoidal homogeneous fluid. Maclaurin’s analytical result for homogenous bodies generalizes to this model and leads to very accurate analytical results connecting the three observables: oblateness (ò), gravitational quadrupole (J2), and angular velocity parameter (q). The analytical results are compared to observational data for the planets and a good agreement is found. Oscillations near equilibrium are studied within the model.
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supported by the National Science Foundation of China under Grant 61271186
文摘Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.
文摘Using embedded atom method and molecular static relaxation method, the core structure of <100>, <110> edge dislocations, <100> screw dislocation, the interaction between point defects and <100> edge dislocation in NiAl intermetallics were investigated. The results show that <100>edge dislocation expands along and orientation on the (001) slip plane. The core structure of <100> edge dislocation on (001) plane is like a 'butterfly', while it is very compact when it lies on {110} slip plane. So NiAl will have a <100>{110} slip system in stead of <100>{100} slip system, as experiments showed. <110> edge dislocation has a more expanded core structure and the atoms of dislocation core distort more heavily. None dislocation dissociation was found in the studied dislocations. The outlines of dislocation core structures change very little after a row of point defects are introduced in them, which can be explained by point defects' little effects on the stress field around dislocation core. The results also show that it is hard to change dislocation core structure by decreasing alloy order using the method of introducing limited point defects into the alloy.
文摘在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(Matern Hard Core Point Processes,MHCPP)对ISAC基站的位置分布进行建模,考虑通信和感知时分复用的系统机制,以典型用户作为研究对象,将其关联到距离最近的基站,分别对通信和感知进行性能指标建模,推导典型用户和关联基站受到的平均干扰功率以及平均吞吐量的下界,并进一步通过仿真验证推导结果的准确性.仿真结果表明:相较于泊松点过程(Poisson Point Processes,PPP),MHCPP对平均干扰功率具有降低效果,通信场景中平均干扰功率降低了30%~43%,感知场景中平均干扰功率降低了91%~93%;随着基站间最小距离的增大,通信平均吞吐量增加,感知平均吞吐量先增后减,在实际场景中需结合系统需求来确定ISAC组网的参数设计.研究结果可为系统设计和扩展性分析提供参考.
