基于嗅觉神经网络仿生模型的纹理图像生成算法

提出了一种基于嗅觉系统生成纹理图像的仿生模型。该模型结构模拟嗅觉神经网络的结构,利用Logsitic函数的混沌特性调整每次迭代过程中的模型参数,使用简单的周期函数作为模型节点的激活函数实现纹理的重复,并引入随机噪声来模拟脑在进行信息处理时的背景噪声。实验结果表明,该模型可以生成丰富而多变的纹理图像,引入的随机噪声也起到了积极的作用,可以明显地丰富纹理图像的变化。此外,模型生成纹理图像的效率也高于传统的BP神经网络模型。     

An efficient optimization method for periodic lattice cellular structure design based on the K-fold SVR model

The design optimization of periodic lattice cellular structure relying exclusively on the computational simulation model is a time-consuming, even computationally prohibitive process. To relieve the computational burden, an efficient optimization method for periodic lattice cellular structure design based on the K-fold support vector regression model (K-SVR) is proposed in this paper. First, based on the loading experiments, the most promising unit cell of periodic lattice cellular structure is selected from five typical unit cells. Second, an initial SVR model is constructed to replace the simulation model of the periodic lattice cellular structure, and the K-fold cross-validation approach is used to extract the error information from the SVR model at the sample points. According to the error information, the sample points are sorted and classified into several sub-sets. Then, a global K-SVR model is re-constructed by aggregating each SVR model under each sub-set. Third, considering that there exists prediction errors between the K-SVR model and the simulation model, which may lead to infeasible optimal solutions, an uncertainty quantification approach is developed to ensure the feasibility of the optimal solution for the periodic lattice cellular structure design. Finally, the effectiveness and merits of the proposed approach are demonstrated on the design optimization of the A-pillar and seat-bottom frame.

     

Visualized CAD models of objects made of a multiphase perfect material

A component, which has a perfect combination of different materials (including homogeneous materials and different types of heterogeneous materials) in its different portions for a specific application, is considered as the component made of a multiphase perfect material. After design of such a component according to the requirements from a specific application, a CAD model for representing it should be built so that its further analysis and manufacturing can be implemented based on the model. According to a new modeling method, this paper further presents the approaches of retrieving and visualizing all the necessary information of each layer of a component from its CAD model. The information includes: (1) 2D geometric boundary of each material region on each layer; (2) volume fraction of each material constituent for each position in each material region; and (3) 2D geometric boundaries of void phases of base cells in material regions with a periodic microstructure. Finally, two examples are given to demonstrate both geometric and material information on the layers, thus verifying the proposed approach.     

基于角色和任务的工作流访问控制模型

提出了一个基于角色和任务的工作流访问控制模型,其基本思想是:角色和权限不直接挂钩而是通过任务把角色和权限联系在一起,然后给用户指派合适的角色,用户通过其指派的角色获得可以执行的任务,然后在执行某个任务的某个具体实例时获得该任务所允许访问的客体的权限,更便于权限粒度的控制和管理。在模型的工作流任务规范中加入了时态约束,表示只能在某个时间段内执行该任务,这样可以保证授权有效时间与任务执行时间尽可能同步。在工作流的执行过程中,系统会保存一个授权基,即任务的历史执行信息,根据这些历史执行信息求出有资格执行任务的用户集,从而实现动态职责分离。     

Periodic solutions of a single species discrete population model with periodic harvest/stock

We discuss a discrete population model describing single species growth with periodic harvest/stock. The theory of coincidence degree is applied to show that the model equation admits two periodic solutions. Under minor technical assumptions, we show that one of these two periodic solutions is positive and attracts almost all positive solutions.     

Almost periodic dynamics of a delayed three-level food-chain model

This paper is concerned with the dynamics of a three-level food-chain model with time delays. By means of Mawhin's continuation theorem of coincidence degree theory, we investigate the existence of positive almost periodic solutions in a three-level food-chain model with time delays. A set of sufficient conditions for the existence of at least one positive almost periodic solution of the model is obtained. In addition, the global asymptotical stability of the almost periodic solution of the above model is also studied. Finally, two examples and simulations are also given to illustrate the main results in this paper.     

周期性干扰的鲁棒切换型控制策略

讨论了一类二阶不确定线性切换离散系统的控制问题 ,应用监督控制技术提出一种新型的适应性鲁棒镇定切换型控制策略。通过将该控制策略应用于磁悬浮轴承不平衡周期性振动的主动控制实验 ,验证了该方法的有效性和鲁棒性     

Reconstruction of surface texture based on spatial information measured with a pen-type texture sensor

Surface texture is one of the important properties for the human to identify objects by touch. Effective reconstructions of textures are necessary for realistic interactions between the human and environment via human–computer interfaces. This paper presents a systematic approach for sensing and reconstructing periodic surface textures. Three significant issues are discussed: a pen-type texture sensor that measures the spatial information based on the measurements of contact forces; an algorithm for the reconstruction of periodic textures based on the obtained spatial information; and the method of incremental scanning to identify the polar spectrum of a surface by limited number of scans. The concept of polar spectrum is introduced to describe the spatial properties of the surface, that is, the relation between spatial frequencies and the direction of measurement. The pattern of polar spectrum is used to facilitate surface reconstructions. Experimental results based on the spatial information obtained with a laser displacement sensor and the pen-type texture sensor demonstrate the effectiveness of the proposed methods for the measurement and reconstruction of periodic textures.     

限幅型非光滑吸振器模型的稳定性与周期运动研究

本文研究具有分段光滑特性的限幅型吸振器模型的稳定性与周期运动. 建立一类限幅型非光滑吸振器的动力学模型,探讨模型容许平衡点的存在性,通过Liénard-Chipart稳定性准则,分析容许平衡点的稳定性. 通过参数变换,将限幅型吸振器模型转化为具有两个切换流形的四维分段光滑系统. 通过计算系统首次积分,获得四维含参分段光滑动力系统在其未扰系统存在一族周期轨条件下的Melnikov函数. 探讨不同参数条件下系统周期轨的存在性及个数,并利用数值模拟方法给出其相图构型,验证理论结果的正确性. 研究结果表明不同的间隙参数影响系统周期轨个数及相对位置.     

Stability aspects of a multifrequency model of a PWM converter

In this paper the stability of a multifrequency model of a PWM converter is investigated. A multifrequency model is a model based on Fourier series that contains as a special case the so-called state space average model. In contrast to a state space average model a multifrequency model may also include so-called higher order harmonics, where the zeroth order harmonic corresponds to the (moving) average. This paper focuses on a specific PWM converter, namely a ( uk converter, and it is proved that a multifrequency model of a ( uk converter with fixed duty ratio is asymptotically stable. This result generalizes the known corresponding result for a state space average model of a ( uk converter with fixed duty ratio. Taking all the harmonics into account the result also illustrates the well-known fact that a ( uk converter with a fixed duty ratio and a finite switching frequency is asymptotically stable in the following sense. If the signals in a ( uk converter do not correspond with a periodic behaviour, they will however do so in the limit, i.e. as time goes to infinity the signals will become periodic, and this limiting periodic behaviour is unique. Although the paper mainly deals with the stability issues for a ( uk converter, it is possible to use the ideas of the paper to derive similar results for other types of PWM converters.     

A separation theorem for periodic sharing information patterns indecentralized control

Optimal decentralized control of a discrete-time stochastic system is considered under a periodic sharing information pattern. In this scenario, controllers share information with one-step delay every K time steps. The periodic sharing pattern is a generalization of the previously studied one-step delay sharing pattern, which is known to possess a nonclassical separation property. It is proven that the periodic sharing pattern has an analogous separation property     

Active noise control using a dual feedforward approach

A dual feedforward controller for active noise control is presented. The first part of the controller is designed to cancel broadband noise, and the second part is an adaptive controller designed to cancel periodic noise. A simple technique to identify the parameters of the broadband controller is developed. An autoregressive moving-average model is used, and it is found that its stability is improved by prefiltering the test signal with a minimum-phase inverse of the secondary noise channel. The periodic controller uses an estimate of the fundamental frequency to cancel the first few harmonics of periodic noise. A computationally efficient adaptive technique based on least squares is developed to update the harmonic controller gains at each time step. Experimental results are included which demonstrate simultaneous cancellation of both random broadband noise and periodic noise     

一类分段线性神经元系统的动力学行为分析

针对一类平面上三分段连续线性神经元模型,研究了边界平衡点的持续性分岔(persistence)、非光滑折分岔(non-smooth fold)的存在条件及一类跨边界周期解.最后,通过施加缓慢变化的周期外激励研究其对边界分岔和系统周期放电的影响.     

基于联合特征和XGBoost的活动语义识别方法

针对以往活动语义识别研究单纯提取时间维度上的序列特征以及周期特征、缺乏对空间信息的深度挖掘等问题，提出一种基于联合特征和极限梯度提升（XGBoost）的活动语义识别方法。首先，挖掘时间信息中的活动周期性特征和空间信息中的经纬度特征；然后，使用经纬度信息通过具有噪声的基于密度的聚类（DBSCAN）算法提取空间区域热度特征，将这些特征组成特征向量来刻画用户活动语义；最后，采用集成学习方法中的XGBoost算法建立活动语义识别模型。在FourSquare的两个公共签到数据集上，基于联合特征的模型比基于时间特征的模型在识别准确率上提高了28个百分点，与上下文感知混合（CAH）方法和时空活动偏好（STAP）方法对比，所提方法的识别准确率分别提高了30个百分点和5个百分点。实验结果表明所提方法与对比方法相比在活动语义识别问题上更加准确有效。     

神经元网络模型的弱信号随机共振检测研究

基于FitzHugh-Nagumo可兴奋细胞耦合后形成的神经元网络模型,对生物神经系统的弱周期信号随机共振检测机制进行研究。以加和网络的双层FHN神经元模型为例,对周期随机共振现象分别进行研究,并应用信噪比、互信息率对比评价方法,结合输出神经元动作电位的发放频率和幅值,从多个角度进行了定量和定性的描述和比较。实验结果表明,双层FHN神经元网络的随机共振响应优于单神经元的FHN模型,且具有更好的稳定性,可以在一定的噪声强度范围内对输入信号进行有效地检测。     

基于联合特征和XGBoost的活动语义识别方法

针对以往活动语义识别研究单纯提取时间维度上的序列特征以及周期特征、缺乏对空间信息的深度挖掘等问题,提出一种基于联合特征和极限梯度提升（XGBoost）的活动语义识别方法。首先,挖掘时间信息中的活动周期性特征和空间信息中的经纬度特征;然后,使用经纬度信息通过具有噪声的基于密度的聚类（DBSCAN）算法提取空间区域热度特征,将这些特征组成特征向量来刻画用户活动语义;最后,采用集成学习方法中的XGBoost算法建立活动语义识别模型。在FourSquare的两个公共签到数据集上,基于联合特征的模型比基于时间特征的模型在识别准确率上提高了28个百分点,与上下文感知混合（CAH）方法和时空活动偏好（STAP）方法对比,所提方法的识别准确率分别提高了30个百分点和5个百分点。实验结果表明所提方法与对比方法相比在活动语义识别问题上更加准确有效。     

Difference games with periodic information structures with application to the worst case design of regulators†

Nash equilibrium strategies of general linear-quadratic two-player difference games with two kinds of periodic information structures are considered. Solution algorithms are developed for problems where the players' information is of periodic open-loop or periodic open-closed type. In the former case the players receive measurements of the state periodically only at the beginning of each interval and in the latter case one of the players has a perfect memory information of the state within each period. The solutions are obtained by recursive algorithms where a series of coupled difference equations of Riccati type are solved repeatedly and where the boundary values of these equations are determined by similar difference equations. A new game theoretic worst case design method based on games with periodic open-closed information structure is then proposed and applied to the design of a state regulator for a pilot process. The results obtained in the example suggest that this new approach can be successfully employed in practical design problems.     

季节时间序列法在IP网异常流量检测的应用

针对TCP/IP骨干网,利用NetFlow技术,提出一种基于业务流量周期规律特性的建模与异常检测方法。该方法通过挖掘骨干网主要业务流量的规律性,结合时间序列分析方法,有效地预测流量的变化趋势,避免了对复杂的流量非线性趋势进行建模分析。     

集中式集群资源调度框架的可扩展性优化

集中式集群资源管理系统既能够确保全局资源状态的一致性亦拥有多种调度模型,因此被广泛应用于实际系统中.但是,当集中式资源管理器在接收并处理大规模的周期性心跳信息时,由于其采用单一节点来维护全局资源状态,所以资源管理器的负载压力急剧增加,导致调度能力降低,影响了集群系统的可扩展性.针对上述问题,提出一种"没有变化就不更新"...     

Dynamic deployment optimization of near space communication system using a novel estimation of distribution algorithm

A robust deployment of the airship platforms is crucial to the performance of the Near Space Communication System (NSCS) in the dynamic environment. In this paper, a multiobjective NSCS deployment optimization model with multi-phased periodic user distribution is proposed. To optimize this model, we propose a local incremental estimation of distribution algorithm with an asymmetrical domination relationship within the multiobjective evolutionary algorithm based on decomposition framework. The conflict between the selection mechanism and the domination relationship is also analyzed theoretically for the first time. To obtain robust solutions under this conflict, the local distribution information of a certain subproblem within several generations is encompassed into a local incremental distribution model. As a generalized form of the existing domination relationship, an asymmetrical domination relationship (ADR), which treats the current and past objective values differently, is proposed to select robust solutions. The proposed algorithm is also tested on four designed problems compared with another four popular algorithms and proves its superiority. Some important parameters are also investigated in the experiments and some guidelines on tuning these parameters are given as well.